The Etruscans were one of the other cultures to live in Italy in the 1st Millenium BCE. They are often overlooked in favour of the Romans (who conquered them), but they were a power in their day and even ruled over Rome for a while early in its history. They were the subject of an In Our Time episode from 2011 which we listened to recently, and discussing Etruscan history and culture were Phil Perkins (Open University), David Ridgway (University of London) and Corinna Riva (University College London).
The Etruscan culture began around 800 BCE and lasted for the next 800 or so years. They lived north of Rome in an area roughly the same as modern Tuscany - the similarity of the words Etruscan and Tuscany is not a coincidence. Their origins are obscure, Herodotus said they came from Lydia (in modern Turkey) and there is some controversial DNA evidence that suggests a Middle Eastern origin but as described by Perkins* this is unconvincing. The study only looked at Y chromosome sequences from modern inhabitants of Tuscany, and it's not clear how (or if) they decided who was likely to've been descended from the Etruscans. Nor did their results give any indication of when this Middle Eastern origin was so it's not clear if it has any bearing on distinguishing the Etruscans from other inhabitants of Italy - after all, most of our ancestors in Europe came via the Middle East on the way out of Africa many 10s of millennia ago! The consensus from the experts on the programme was that this was all rather implausible, and it was more likely that their immediately preceding history was as inhabitants of Italy. Interestingly, however, their language is not an Indo-European language and has no modern relatives.
There is not much surviving textual evidence from the Etruscans themselves - most of what is written down is by the Romans. There is no surviving Etruscan literature at all, and only a few inscriptions. These are in both temples and tombs and written in a modified Greek alphabet, but they just tend to name people or gods and give genealogies. Why there is no literature is an interesting question with no clear answer. It seems implausible that they didn't produce any written literature - given the time and place where they lived, and the level of sophistication, wealth and power shown by the archaeological evidence. This implies that the literature was destroyed - and one persistent theory is that there was a purge during the time of the Roman Empire (after Claudius was Emperor, I think they said) to wipe out the memory of their rival civilisation. Nobody on the programme was willing to say that this was true, but they seemed to agree that it was pretty plausible it's just there's no evidence for it one way or the other.
In contrast to the paucity of texts from the Etruscans there is a wealth of archaeological evidence. The way they phrased it on the programme was that in Tuscany it's not the Roman ruins you go to see, it's the Etruscan ones. Even by the standards of Italy this is an area rich in ancient sites. Tombs and graveyards are the main sources of information about the Etruscans - these sites include grave goods, wall paintings and some inscriptions. A few temples and city buildings have also been excavated.
Thinking of the Etruscans as a state is anachronistic. Like Greek culture of the time they were a group of independent city states which shared a common language, culture and religion. Their religion is only known from what the Romans wrote about it, but it appears to've been different in emphasis to the surrounding cultures. The origin story for their religion is someone (a mythical/mystical figure) teaching them how to interpret the omens. The worshipper doesn't pray to the gods and ask them for help or favours. Instead one's religious duty is to interpret the messages the gods are sending via signs & portents - a one way route of communication.
The 6th Century BCE was the heyday of the Etruscan culture. The hills of Tuscany have rich mineral deposits including both tin and copper. Together these metals make bronze - and so were much sought after at the time. The Etruscans could not only outfit their own people with weapons and tools, but also traded extensively around the Mediterranean. They were later called a warlike people, but the consensus on the programme was that there's no evidence of them being worse than anyone else at the time. This was, after all, a warlike period. Their artistic culture is sometimes dismissed as "copying the Greeks but getting it wrong" but the experts were unanimous in declaring this bobbins (rather more politely tho). The Etruscans had a sophisticated artistic and architectural style, which had clearly been influenced by the Greeks but was also uniquely their own. They did often employ imported Greek artists, as they were seen as the best of their day. Ridgway referred to their style as being less bland than the Classical Greek style.
The Etruscans had an influence on Roman art, culture and politics. This is not surprising, as Rome is not very far from Etruscan territory and early in its history it was "just another city state" rather than being the juggernaut of empire that it later became. Early in Roman history they were even ruled by one of the Etruscan city states. Later however the Romans conquered and assimilated the Etruscans. As pointed out above, the Etruscans weren't one cohesive unit so the Romans could conquer them a bit at a time rather than face all of them en masse. They had influence in the Roman political arena much later than one might expect, given they were conquered by Rome around the 4th Century BCE. The Emperor Augustus was supported during the civil war (preceding him becoming Emperor) by several old Etruscan families. These families were the aristocracy of the old Etruscan city states but had been assimilated into the Roman society and political elite by this point. However they were seen as a distinct and influential cultural bloc, that was necessary to get "on side" if you were making a power play. Later still Claudius was married to the daughter of one of these families (who persuaded him to write a history of the Etruscans, now sadly vanished without trace).
I knew pretty much nothing about the Etruscans before I listened to this programme, beyond the simple fact of their existence. I know the British Museum has a room displaying their culture, and this programme has made me want to have a proper look at it sometime.