Answer
If al vertical lines pass through at most one point on the graph, then the graph represents a function. Otherwise, it is not a function.
Work Step by Step
The vertical line test is used to know if a given graph represents a function or not.
$\\\\$If all vertical lines will pass through at most one point on the graph, then the graph represents a function as it means that each first coordinate is paired with only one second coordinate.
$\\\\$On the other hand, if at least one vertical line passes through more than one point on the graph, then the graph does not represent a function as it means that there exists at least one first coordinate that is paired with more than one second coordinate.