What are cron jobs?
Cron jobs are tasks that run on a schedule, for example every night.
What it is
A cron job is a task with a clock. Clean up every night, fetch something every hour, build a report once a day. It runs even when nobody has the site open. The app does not wait for a click.
The site can look perfectly fine while the nightly job has not run for days.
What it is made of
The name comes from cron, the scheduler on Unix servers. The idea is older than any one host: one line says minute, hour, day, and the command. In containers and platforms the same thing is often called a scheduled job or a worker. The question stays: when, what, and what happens if it gets stuck.
What goes wrong
A task that takes longer than the gap until the next run otherwise starts twice. A task that aborts has to be visible to someone, or the report is missing and nobody notices. Logs and a clear end, success or failure, belong to it.
What you otherwise look after yourself
For that you need a process that watches the clock, separate from web requests. If that process fails, nothing happens at night, and in the morning the site still looks normal.
How it shows up on MainPath
MainPath takes on these scheduled tasks with the project, instead of you maintaining a separate crontab on every server.