What does the following equation represent?

What does the following equation represent? Explain. p2+ 2pq + q2= 1

p2 + 2 pq + q2 = l
This is called binomial expansion of (p + q)2.
The extent of evolutionary change is the difference between the value of frequency measured (frequency obtained) and the value expected. The disturbance in genetic equilibrium (Hardy-Weinberg equilibrium) would result in evolution.