domain represents the x values so for example in a diagonal line that continues infinitely, the domain is all real numbers or (-infinity, infinity)
range represents y values so it would also be all real numbers or (-infinity, infinity)
let’s say there is a line (refer to pic) that moves ONLY from point (-3, -1) and (2, 2)
the domain would be [-3, 2]
we use brackets because it’s a real number unlike infinity (also because it’s a closed circle on the graph; if the graph had an open circle you would use a parenthesis)
and the range would be [-1, 2]
if you have any more questions about this explanation feel free to ask!