ANSWER
Domain = {6, 5, 4, 3}
Range = {-2, 0, 2, 3}
Yes, it is a function
EXPLANATION
We are given the relation:
{(6, -2), (5, 0), (4, 2), (3, 3)}
The domain of a function is the range of values for which the function is valid while the range of a function are the values which are obtained from a function.
Basically, the domain contains the input values while the range contains the output values.
When the domain and range is written in the form above (x, y), we have that the domain is the x value while the range is the y value.
Therefore, for the relation:
Domain = {6, 5, 4, 3}
Range = {-2, 0, 2, 3}
The relation is a function because each value of the domain produces only one value of the range.