Infestation: Survivor Stories' inventory screen is the primary means of accessing the items inside of your backpack. It also features a display for the type of backpack you are carrying, the maximum weight you can carry, and how much you are currently carrying. The inventory screen can also be used to change the weapons you currently have equipped as well as headgear and any armor.Also, you can "use" your consumable items like the "Chocolate Bar" from the inventory screen.
The inventory system was first introduced in a forum post by Sergey Titov
"We'll cover Inventory system today. First of all - I've censored part of the image that contain some debug information. To get to inventory you can either press hotkey ( 'I' by default ) or by pressing ESC to get to pause menu and selecting "INVENTORY" tab. Content of the inventory screen depends on type of backpack you're using. You'll start with really small backpack that can only hold 8 unique items. Please note that as you can see some items can be stacked, so lets say if you have 10 magazines for your gun or 10 bandages, they'll take just one slot. When you'll find new backpack in a world, you'll be able to change your current backpack to new one. Old backpack will become just and object in a world, so you can still carry it in yout backpack ( ie it'll take one slot ) and use for trade or something. When you press CHANGE BACKPACK buutton it'll show you what other backpacks you have in your current backpack or in your global inventory ( this option is only available in Safe settlements ). As you can see I don't have any other backpacks available. On top part of the screen you see four "hard" slots reserved for certain type of items. Those are slots that shows what's equipped on your character. First slot if for guns, second is for melee weapons, third is for vests, armor ( if you lucky to find one ) and head gear. Below you see information about weight you currently carry and maximum weight your character can carry. Those numbers doesn't depend on type of backpack you're using - they're depends on your character TRAINING. Below that are four "hot slots" - ones you see in your quick access bar in HUD. You can move items between slots by just dragging and dropping them where-ever you want them. If you want to do some action with item you can access "USE" menu for item by right mouse clicking on items icon. Content of this menu varies between items - as you can see in case of vaccine I can either use it or drop it. Since I have only one vaccine shot, there's no option for "mass drop" - ie if you'll have for example 10 items and want to drop them at one - you'll have a special menu option for that."
There will be an global inventory available for all your characters. You can store your items in the global inventory which every character of you can access. If you find a nice weapon for one of your new character then store it in the global inventory. In the main menu of Infestation: Survivor Stories you can then give the weapon to another character.