How it works...

The crontab line consists of a line describing how often to run the task (first six elements), plus the task. Each of the initial six elements mean a different unit of time to execute. Most of them are stars, meaning any:

* * * * * *
| | | | | | 
| | | | | +-- Year              (range: 1900-3000)
| | | | +---- Day of the Week   (range: 1-7, 1 standing for Monday)
| | | +------ Month of the Year (range: 1-12)
| | +-------- Day of the Month  (range: 1-31)
| +---------- Hour              (range: 0-23)
+------------ Minute            (range: 0-59)

Therefore, our line, */5 * * * * *, means every time the minute is divisible by 5, in all hours, all days... all years.

Here are some examples:

30  15 * * * * means "every day at 15:30"
30   * * * * * means "every hour, at 30 minutes"
0,30 * * * * * means "every hour, at 0 minutes and 30 minutes"
*/30 * * * * * means "every half hour"
0    0 * * 1 * means "every Monday at 00:00"

Do not try to guess too much. Use a cheat sheet like https://crontab.guru/ for examples and tweaks. Most of the common usages will be described there directly. You can also edit a formula and get a descriptive text on how it's going to run.

After the description of how to run the cron job, include the line to execute the task, as prepared in Step 2 in the How to do it… section.