I don’t know what an “app” is. Will my lack of knowledge hurt me in the future?
You will probably get a better answer from somebody else, but here’s my understanding.
An ‘app’ (probably short for application or appliance or something) is a little program that can run on your smart phone (and maybe other things like i-pads or even regular computers not sure) and it will do all sorts of different things.
My daughter had one where she could keep records on her baby, when he ate and how much, when did he got to sleep, diaper changes (and what was in them!), etc. It synched up between her phone, her hubbys phone, her i-pad, etc. It was actually great, very easy to use and if we were baby sitting you could look back and see when/what he’d eaten the day before, etc. And of course she could keep tabs on us too. I think that cost her about $15-
And almost everyone has the one that let’s their phone become a little flashlight, using the flash for the camera.
Some are free, many cost only a dollar or two.
They are pretty cool, although I don’t like the alarm one I put on my android phone.
I gotta say, I resisted a long time but those smart phones are really great, they are like swiss army knives of computing.