share functions between server and client

Hi, I'm seeking clarification on how functions are shared between the server and client. According to the documentation, 'Operations' (like actions) are used to modify data in the database, with the functions being executed on the server side.

My question is: can 'actions' be utilized to create server-side functions that do not interact with the database, or is it necessary to write the logic separately and then import it into client files? If the latter is correct, how does Wasp differentiate between server-side and client-side code?

Thank you for your support!