Handouts are resources that a participant, often the GM but not limited to the GM, wants to share with the group. The intent of a handout is to give other participants ongoing access to some piece of information. Consider it analogous to printing out a sheet that you hand to each of the participants in a face-to-face game. Creating and sharing handouts is not limited to the GM. Anyone can share a handout with the group. Currently, only images are supported as handouts. Additionally, consider Alternate Ways of Sharing Info, below.  

Handouts in Face-to-Face Games

In a face-to-face game, handouts allow you to show the players that spooky old mansion, or the monster bearing down on them, or that important NPC, without spending the time and ink to print out pictures before the game. Because handouts are presented in their own windows, it's very easy to open them and drag them to a secondary display for presentation to the group.

Actions on Handouts

To create a handout, go to the Handouts tab and select the "Add Handout" button. This prompts you to select a file from your local disk and puts it in the handouts gallery for potential sharing. A newly-created handout is not automatically shared. 

To share a handout, right-click on it in the gallery and select "Share". This will open the handout in a popup window on each of the other participants' computers and make it available in their handouts gallery. If they close the popup window, they can get back to the handout through their gallery--at least until you unshare it. Handouts are shared with all participants or none. 

To unshare a handout, right-click on it in the gallery and select "Unshare". This removes it from the other participants' galleries and closes the handout's window if a participant has the handout open. You can use this to make some piece of information that's been taken from the characters unavailable to the players as well. Or you can use it just to tidy up the set of resources they're dealing with. Unsharing a handout does not remove it from the game. It simply makes it unavailable to the other participants.

To remove a handout from the game entirely, right-click on it in the gallery and select "Remove". This removes it from your handouts gallery and automatically unshares it, removing it from other participants' galleries.

Alternate Ways of Sharing Info

Sometimes, a handout isn't the best way of sharing information. Handouts are best when you want to give resources to other participants for reference however and whenever they want. For more control over how material is presented, it's often useful to use a shared tabletop. Tabletops support objects like images, notecards, and text notes with rich formatting. You can size and arrange these objects on a tabletop and share it with other participants. For example, I'll often use a "Recurring NPCs" tabletop and a "Player Notes" tabletop.