Slytherin

Founded by Salazar Slytherin

In establishing the house, Salazar instructed the Sothing Hat to pick students who had a few particular characteristics he most valued. Those characteristics included cunning, resourcefulness, leadership, and ambition.

Many Slytherin students tended to clique together (often acquiring leaders) which further exemplified Slytherin's ambitious qualities.

The founder highly valued and favored pure-blood students and the Sorting Hat admitted that it could be a factor when being sorted. Students of any blood status could be placed in the house. However, a Muggle-born student from that house was considered to be quite rare.

The emblematic animal of the house was a snake and the house's colors were green and silver. There were two notable heads of the house; 

Slytherin corresponded roughly with the element of water due to serpents being commonly associated with the sea and lochs in western European mythology, as well as serpents being physically fluid and flexible animals. Similarly, in Celtic mythology, water is seen as a portal to another world, leading some to believe that the element was chosen to symbolise a Slytherin's dream for a world in which their goals and ambitions had finally been achieved. Others speculate that it was chosen to symbolise many Slytherins' hope for a pureblood-only wizarding society.

The colors also corresponded with waters around lakes and lochs often being green, and silver being often associated with grey rainwater.

This information is from Harry Potter Wiki - https://harrypotter.fandom.com/wiki/Slytherin