By far the most common application to use with remote.it is SSH, or network console. SSH gives you direct access to your device's command line. SSH also enables SCP file transfer.
VNC is "Virtual Network Client" which gives you access to your Linux device's graphical desktop, if it is running one.
RDP (Remote Desktop Protocol) is similar to VNC although it is typically used on Windows systems.
Samba lets you access Windows drives on a LAN from a Linux PC