Questions about Preheaters

Hello,

I own a hot air reflow station and I saw this guy on youtube using a preheater.
Preheater let me guess just warms up the pcb.
Do I really need to preheat the board to mount some components on the pcb?
There must be pros and cons for a preheater.

Is it worth buying one?

Ben

Perheaters have been discussed on ETO in the past year.

Would be nice to have. Few if any of us with home hot air units have them. It takes a bit longer to solder a part without.