A ping beacon is flashing highlight on the mini-map. It is placed by one player to bring attention to that location to the other co-op partners they are playing with.
This is a common function in co-op games.
Toggle combat mode (What does it mean by "MODE")
When outside combat, pressing this key will draw your weapon. Pressing it again will put your weapon away.
Toggle Game Master game pause
When playing in GM mode, if the GM presses this it pauses the game for everyone. Press it again to un-pause.
Switch back and forth between controller input and keyboard/mouse input.
Toggle Actions bar on hot bar
Pops up the menu for the Action icons so that you can put them on your hotbar if you want.
Open and close the crafting window.
Open and close the character info window.
Set Start Point is a command used in the design of a GM mode module. It sets the start point within a zone map for the players when they travel to that location on the world map.
Toggle Map and toggle overview map
Open and close the Map.
Open and close the Waypoint menu (in the GM mode campaign editor).
Toggle the item generator panel.
Open and close the Item Generator window (in the GM mode campain editor).
It is not the game's job to teach you basic English.