Below is important terminology for vertex form of parabolas!
Optimal Value (Max. / Min. Value)
The Maximum value is the highest point of the parabola while the minimum value is the lowest of the parabola. If the parabola has a max value, it will open downwards. If it has a min value, it will open upwards.
How do I Label it?
Set your x at 0 and plug in the y value