After you make a connection, you'll want to use it in your client application. Here are several articles which describe using remote.it with the most popular applications.
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 and SFTP 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.
A web, or http connection should be used for any browser based application, such as:
A web browser
LuCI administrator UI on OpenWRT
PiHole DNS ad blocker
Samba lets you access Windows drives on a LAN from a Linux PC