What is really meant by "programming" when people say they like to use linux for it?

I've always wanted to understand what is actually meant by this. I have wanted to get into programming for years, did some basic python and c, but could never really progress. Not necessarily a linux question but I know since most distros come with libraries already, it's popular to use for programming.

I have trouble understanding what people are actually programming if it isn't their job. Like, you go to your computer and start working on...what? I don't know enough to make an entire program or debug a game, so im just unsure what people do especially when starting out.

Also I don't really want to learn it for a job. I just want to learn it to know it. But im not sure how to apply it to anything realistic.