I have found that in general a straight edge knife is best for chopping vegetables and cutting fruit, however, a serrated knife works much better for bread (like Louis said) and some waxy-skinned vegetables and fruits or those that are some soft on the inside. This is especially true with tomatoes and bell peppers in my experience.

I know very little about cooking, but I do know:

1) Serrated works better for bread. For vegetables and a lot of other things though, I prefer a giant, straight-edge (sharp sharp shap!!)

2) Cutting technique: Keep the knife point on the cutting board and rotate the knife up and down to chop things.

3) Don't chop off your finger.

Here's a collection that you might enjoy :) https://grokker.com/cooking/collection/cooking-and-baking-technique/603ad570b356ab7d31b49206