How does autorun programs work in Linux (ubuntu)?

Question

System administration

If I understand correctly, then for the program to start at system startup, it needs a daemon. Why can't I find a daemon for programs like skype or dropbox then?
How do they work without daemons?

Answer 1

Because a daemon (well, or in systemd terminology, a "service") is not about desktop applications. Skype and dropbox do not start at system startup, but after you log in. What starts at system startup is console.