Answer: No, this isn't a function.
Why not? Focus on the two points (0,2) and (0,4)
We have the x value x = 0 show up twice. Any time x repeats itself like this, it leads to "not a function" as the result.
In other words, the input x = 0 leads to multiple outputs y = 2 and y = 4 at the same time. A function is only possible if every x input leads to exactly one y output.
If you are a visual learner, then plot all of the points on the same xy grid. Then notice how (0,2) and (0,4) fail the vertical line test to show we don't have a function.
Side note: The y values can repeat themselves in a function.