Excuse my beginner terminology as I work my way up the road biking learning curve...

I have a Shimano 105/Ultragra mix on my bike. To shift the front derailer, I have to push in twice. (But not for the rear.) My husband says this is for "half" shifting... or somethinglikethat. I barely notice it anymore, but I don't understand why. Why would I only want to shift halfway?

When I first got the bike, I get doing it *incorrectly* (only pushing in once) and kept dropping the chain. I thought something was wrong with the derailer!