A standup is generally what it sounds like - the entire team stands up together and quickly/briefly cover what they have worked on in the last 24 hours. This can be as simple as "still working on x", or "i need x from y to continue".
Some places don't manage standups well at all, and that is one of the big problems with standups in general - they become status meetings and take too long. When done right, they are very useful as you quickly know what everyone is working on and if someone might need your insights on something (which should then be a separate meeting and not covered in the standup).
There are a few main features of standups that, if abused or ignored, can lead to awfulness.
- They're supposed to be short, very short. A few minutes at the most. They do not work for large teams (20 people giving a status update is a lot), and if you find yourself having 20-person standups it's time to think about if you should be breaking them into multiple independent standups.
- Managers aren't present, or aren't allowed to speak. This is an opportunity to ask questions, ask for help, describe what you're working on, to other members of your team, not to justify what you were up to yesterday to your boss. It's sharing, not reporting. This part is key.
- You don't troubleshoot in a standup. If you say "I can't figure out why I can't Foo module Baz", there shouldn't be a discussion about it, but someone else might go "I've worked with Baz a lot, let's take a look together after standup.", or later in the day someone might go "Oh hey, that problem you were having with Baz? I think I know what's happening." - this is the ideal intent of standups. Very quick snippets that highlight certain things in everyone's minds.
- It doesn't need to be documented. It's not a meeting, you don't need to take down minutes. Actual tracking of work done occurs separately (your scrum master should be doing this).
Some places don't manage standups well at all, and that is one of the big problems with standups in general - they become status meetings and take too long. When done right, they are very useful as you quickly know what everyone is working on and if someone might need your insights on something (which should then be a separate meeting and not covered in the standup).