There are a few different ways this can play out.

As mentioned above, some people have an annual salary that is divided into 12 equal chunks.

For those who are hourly and there can be any number of paydays.

Some jobs pay every other week on a set day of the week.
Some jobs pay every week on a specific day of the week.
Some jobs pay out every month on the final day of the month, or the final “business day” of the month.
This one had a job that paid on the 5th and 20th at one point.