Consumables provide a temporary benefit to Ryder at Ryder's time of choosing. Different consumables provide different temporary benefits.
The Consumables screen can be accessed at any Loadout terminal. The Consumables screen initially allows equipping two consumables by default. Additional Consumables slots can be unlocked through the Military cryo pods Always Prepared and Versatility.
Additional consumables can be found during exploration, looted from enemies, and purchased from merchants.
Each type of consumable counts as one item (7 total items) towards the Inventory item limit as long as Ryder has one of each consumable type. 50 Backup Life Supports only count as ONE item and so on for the other six consumables.
Consumables items selected on the Consumables screen make that Consumable available for Ryder to use during gameplay. Ryder can continue to use a Consumable item (one at a time) until the Consumables supply in question is exhausted.