Help analysing this passage from Silman's book

I have been reading "How to Reassess your chess" by Jeremy Silman for last few days.

In one of the chapters of that book,while trying to explain the position given in the diagram he says "Black will play to control f5 square,thereby freezing White's pawns.An attempt to play g2-g4 and fight for control of f5 would severly weaken the White king's position."

I don't understand what is so important about f5 square that controlling it will freeze White's pawns.Can anyone explain?

hahahahaha

He probably means white could try to push with f4 and possible g4? (g4 is too risky for own king safety) and try to create a pawn front, but tbh there isn't so much going on here and i am not really impressed with this example by Silman.

Silman makes it sound White has some threat by playing for example: O-O 2. Ng3 Qd7 3. Qd3 Rad8 4. f4, with the idea to push f5 later, but it is all not that impressive. He just outplayed some amateur.