The Loading Screen is a pre-game screen where summoners wait for everyone's game to be ready to start.
You can only see Champion Mastery and player rank of players in your own team. The Mastery 5 emblem is the red badge on the upper-left of the image here.
The summoner can also see their own ping. So while the loading screen is active, they can solve problems before the game starts. This is the green number 43 and dot on the bottom-right of the image here. An extremely poor ping will show as yellow or even red. When the player loses all connection to Internet, their ping will always show as an orange 500 ping.
The loading progress of each summoner can be shown below the ping as a percentage, and is visible to all players on both teams.
Starting with the July 2017 changes to honor, a player who has received honors from their entire team in the previous game will have an icon in the top center (not shown in the image).
During the loading screen a player can use their computer even if the loading screen is in full screen. The user can use
Alt + Tab on Windows to move to other windows. If there's not any other window, he/she can use
Windows + D to get to the desktop.