What are the Items on the right side of the screen?

Ah, you've spotting so helpful items to see you through the Nights. These items can really turn the tide when your Survivors are getting overwhelmed. The items you can use doing the Night are:

• Grenade - you can throw this anywhere on the map. It's best to hit a horde to do maximum damage.
• Molotov - you can throw this anywhere on the map and it has a burn effect which damages enemies over time.
• Flash Grenade - using this on Zombies causes them to be stunned momentarily. Best to do this when you have Survivors in range to pick them off while they are vulnerable.
• Flare - place this anywhere on the map to draw nearby Zombies to it for a short period of time
• Repair Kit - you can use this on any building in your City so long as it has not hit 0 remaining health to regenerate its hit points somewhat.

At first, you can carry 10 of each of these items. You can only take 3 items into a battle at any time. 

You can find more on missions and buy them for Gold should you run out during a battle.