Just above the tabbed area for maps and tabletops, there's a panel that holds the portraits of player characters and the non-player characters that are part of the current scene. When the GM makes a character public, that character's portrait shows up in the portrait bar. This lets all the players see the characters that are part of the scene, helping everyone engage with them. 

Things you can do with characters in the portrait bar:

  1. Drag characters down from the portrait bar to a tabletop or map. If you drag a character to a map, a character token is created for them. 
  2. Double-click on a character portrait to open up the character editor.
  3. Right-click to bring up the context menu from which you can edit or remove the character or give control of the character to another participant.
  4. Reorder the portraits (The order is for your benefit only, not shared--I use this sometimes for my own private initiative order, or for initiative order in face-to-face games.)

Removing the character doesn't delete it from the game, it removes it from the scene, which means that it's no longer in the portrait panel or available as a persona in the chat window. The character is still in the game and can later be made public again, which returns it to the portrait bar and makes it available as a persona in the chat window.

You can also drag the bottom edge of the portrait bar to make it bigger or smaller and the portraits scale accordingly. I like to use a bigger portrait bar for roleplay-heavy games. If you turn off "Lock Layout" (shown on this same screenshot), you can detach the portrait bar and drag it somewhere else, such as to another monitor.

Finally, if you just down like the portrait bar, you can hide it through the "Character Portraits" pulldown on the "Layout" group of the "Main" ribbon, also shown in the screenshot above.