In very simple terms, a process is a defined set of tasks, which are operated to reach a specific goal.
Let's take the example of an accounting system of a big company. Not all users of that system may see all data! So an authorization process is defined. The future user needs to fill a request form, which is then sent to an approver (clearly defined as well). Once this is done, the requestor's profile is created in the accounting system. The requestor is then informed, may log in the system and see the data to which they have been granted access only.
A process can also document how/where files should be saved on a shared drive by the members of a same team.
They are many internal processes.
Getting an external audit of your internal processes may identify areas of waste and improve your business practices.