Good morning mslady. Topping and fimming are very simple. Topping is just as it sounds--you simply cut the top part of the plant off. Some people will clone this.
Fimming is like a mini-topping where you take just a fraction of the growing tip.
When you fim or top, you will end up with 2 (or more) growing tips rather than 1. Every growing tip that you trim will "split" and resume growing with 2 tips. I personally prefer fimming over topping.
This might help you: hXXp://www.marijuanagrowing.eu/the-fimming-tutorial-t36632.html