Full Tunnel
All your traffic get send to the VPN server and if you aren’t requesting a server in its LAN it forwards it to the internet and will send the answer back to you.
VPN-Client <-------> VPN-Server <-------> LAN-Server
\---> Internet
Good for Security (The attacker just sniffs SSL-Packets send/received to/from the VPN-Server)
Split Tunnel
Just your traffic depending the server within the LAN of the VPN Server get send directly to it else your request will be send straight to the internet.
VPN-Client <-------> VPN-Server <-------> LAN-Server
\---> Internet
Good for Performance (The VPN-Server will get less traffic, just addressed to its local servers)