gel is when it heats up and if you don't have it covered you can see it kinda turn vaseline like, then it will go solid again. It can be disturbing to see because you think it's going to stay that way.
Gel isn't a requirement in soapmaking. As a matter of fact a lot of soapers don't want GM soaps to gel at all. I only have a preference for not gelling with OMH and some of the bars I do where gel will make the color morph.
In general I'm of the attitude, "If it's gonna' gel, it's gonna' gel!"
If you want your soap to gel, insulate it with newspapers and old blanket. Warning it can get very hot this way and sometimes will cause cracks in the tops of your soaps, I have had soaps go into gel right in the pot.. Depends on the temp your oils and lye liquid is when you mix them together.. Gelling can also burn off scent and morph it, especially if the flashpoint to your scent is low.. So flashpoint of scent is nice to know before you make your soap.. I am with Bethany on this, I don't gel most of my soaps, I don't insulate milk soaps, so that I don't have to worry about color or fragrance morphing into something nasty, but if it does gel then fine.
Some books will tell you that your soap HAS TO GEL, this is not true.. as long as you reach trace..