There are many types of drywall compound (mud) for different use-cases and skill levels. The premixed bucket stuff sets by air contact - this stuff is usually more forgiving and sandable, just be ready for some shrinking and being patient with allowing to dry fully. The all purpose, lightweight, plus-3 stuff can do most jobs. Many pros will use powdered "hot mud" that sets by chemical reaction - you'll see numbers like 90mins, this is time you get to use it (assume you'll actually get half that before it gets weird). They use this because they are on a job and can get multiple coats done in a day but it takes more skill to get it right. Those are usually less forgiving and harder to sand. Also bucket mud goes rancid after sitting, but what you need for the job but don't expect it to be there for next project.

For the odd small drywall repair around the house, I like to keep on hand a small packet of 15 minute mud powder. You can mix up a little, apply it, and then sand and apply another coat soon after, so you can get the whole job done in an afternoon. And it never goes bad.