Explanation:
1. Vertical Line Test: By definition a function can only output 1 value for each unique input. So if I were to put a vertical line on a graph it should only intersect one point, if it intersects two, that would mean there is 2 outputs for 1 input, so it's not a function
2: Term
3: Sequence: I don't really know how to explain this besides it's literally the definition
4: Relation: This can also be a function, but it it doesn't pass the vertical line test, it's just a relation
5: Solution: A solution to an equation is just what value makes an equation true (both sides equal)
6: Variable: The value varies, it can be anything, depending on what the equation is, so for example y=mx+b, the value of y varies depending on the value of x (and also m and b obviously, but those are constants)