Items can be found in chests around the map, or dropped by a sacrificed survivor. These provide an opportunity to turn the game to your favour. For example: a health kit will allow you to heal yourself, or heal others faster. A tool box will allow you to sabotage hooks or complete generators faster. Each item has an amount of “charges” which decrease as the item is used. Should these charges be used entirely, the item is lost. Items are also lost if you are sacrificed unless a certain offering is used, so use them wisely.
You can change how items work by using add-ons, which can add more charges to an item, or increase the speed of certain actions. Add-ons will also affect a killer's power in certain ways. Check what each item and add-on can do by hovering over their respective icons in your loadout