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Historically, [cron](https://wiki.archlinux.org/title/Cron) was the main way to schedule tasks on Linux. Briefly, there will be some file like `/etc/crontab` which will contain one line for each task. The line starts with a schedule string and a shell style command. 

The schedule string specifies on which minutes, hours, days and months the task should run. When the cron daemon is running, whenever it detects that a time matching the schedule is reached, it executes the command.

When a cron schedule is missed, it's missed. Vanilla cron only cares about what happens when the machine is on. There are extensions like anacron which deal with this edge case.

Systemd timers were meant to replace cron, so many distros now consider cron obsolete and don't install it by default. However, there are programs like cronie and fcron which you can install and obtain the same functionality.

The caveats with cron are:

* When commands fail (cron looks at the exit code) they "send an email". This is not an actual email over the internet, but using an ancient internal mail functionality of Unix, to send it to your Linux user account's "mailbox". These days most people do not understand how this works and get confused by it.
* There is little support for dependencies between tasks, you will have to bake that into your script instead.
* AFAIK crontabs require sudo to edit, and you're not even supposed to edit them directly but use `crontab -e`. Sucks if you were hoping to replace it with a symlink to your dotfiles repo.