What is the domain and range and function then can u explain how u did it and you

The domain is

and the range is

Domain is x values (horizontal axis), while range is y values (vertical axis). On a line like this one, domain is calculated from the left most point to the right most, while range is calculated from the down most to the upmost.
Because this line is a solid line rather than a dotted line, less than or equal to

signs are used rather than just

less than signs.