I'm running a bitcoin full node (bitcoin core) via Tor. I noticed I have only outbound connections (using maxconnections=16 in the conf file), but not even an inbound one. So which is exactly the difference between inbound and outbound? I'm able to regularly receive update tips and relay my transactions to the network however. Furthermore, I set the onlynet=onion option, so I should exclusively receive from and relay to onion addresses
When your client start the connection with another peer it is outbound, otherwise it is inbound.
If you want to be sure that your tor node is properly setup and that other peer can connect to you, check: https://en.bitcoin.it/wiki/Setting_up_a_Tor_hidden_service