You type tldr and then some command. For example, tldr tar. It gives you a small list of examples and common use cases for the command.

I find myself using tldr a lot since finding out about it. It’s just so useful for commands that I don’t use enough to commit to memory.

I’d say it depends on what you do and how much collaboration with other people is involved. I have always used standalone clients, and I’m not a fan anything web browser based (or cloud in general). I started using LibreCalc instead of Excel for my job a few months ago. Now that I got used to it, I love it. It loads faster, has regex out of the box. Excel has already become quite enshittified, in my opinion.