Examples

Frequency Expression Description
Every 5 minutes "*/5 * * * *" Checks for new data or status updates every 5th minute (0, 5, 10...).
Every hour "0 * * * *" Runs at minute zero of every hour (e.g., 1:00, 2:00, 3:00).
At midnight "0 0 * * *" The classic "Daily maintenance" time for starting clean the day.
At 3:00 AM, the week-end "0 3 * * 0,6" "Daily maintenance" but maybe at a better time for your own stuff, week-end only.
AT 9:10 AM, on workday "10 9 * * 1-5" Runs at 9:00 AM, but only Monday through Friday. Good for "Daily Standup" alerts.
On Monday "0 0 * * 1" Runs a cronjob at midnight, the first day of the week, to start fresh.
The 1st of the month "0 0 1 * *" Runs a cronjob at midnight, the first day of the month. For something like Invoices, etc....
Annual Backup "0 0 1 1 *" Runs once a year at midnight on January 1st.