Most roguelikes allow the player to have an inventory of items to use at his/her convenience. The way the inventory works differs quite a lot between different games.
The inventory is in most roguelikes represented as a list of items, sometimes categorized by item type. Some roguelikes limit the inventory to a specific number of items while others limit the inventory to a specific weight or volume of items carried (based on the character's strength).
In some games there is no difference between the player's inventory and the wielded/worn equipment while others have one list for the inventory and one for the equipment.
It is also possible for characters other than the player (aka "monsters") to have inventories. In some cases these are merely items carried, but usually the implementation of monster inventories is done in order to have monsters use items.