frameRate() returns the number of frames per second.
That's the number of times draw() runs in a second.
p5js attempts to reach a frameRate of 60.
Take care with the spelling: capital R in the middle
It can also be used to set the target frameRate.
frameRate(30) will set the target frameRate to 30.
The frameRate can never exceed 60.
0.5 means 1/2 frame per second = 1 frame every 2 seconds