One of the first skills that any player of NetHack needs to know is how to use the inventory.
Press i to see your inventory, which is a list of all items that you carry.
Carrying too many items makes you burdened or worse. Also, you are limited to 52 stacks of objects (corresponding to 26 uppercase and 26 lowercase inventory letters), a quantity of gold (which will occupy a special slot labeled '$' if necessary), and, if you pick one up while your inventory is otherwise full, a load stone in a special slot labeled '#,' even if you are strong or the objects all have low weight. If you find a bag, then you can hold more items.
Implicit inventory itemsEdit
In addition to those items listed with the i command, the hero is assumed to be carrying a wallet (examinable with the $ command), a backpack ("A <foo> crawls out of your backpack!"), and a knapsack ("Your knapsack cannot accommodate any more items."). The knapsack/backpack and/or wallet are among the more remarkable objects in NetHack, even though so little is said about them that they go unnoticed by many players. They are all utterly impervious to fire, shock, corrosion, cursing, or any other kind of degredation. Whatever weight they may have is a matter for speculation only, as they can never be dropped. More worrisome, these items can not be greased to prevent water damage to their contents, as can any sack. The carrying capacity of all containers in NetHack is a subject to inspire much wonder, but the knapsack is perhaps most striking of all containers in this regard: it is capable of holding 52 distinct stacks of items, without regard to how many items are in each stack. If a player were able to contrive to have 52 distinct versions of, say, scrolls, that would be the complete carrying capacity of the knapsack. But, strength allowing, a player could carry 52 copies of a single scroll (of known beatitude), and still have room in the knapsack for 51 other stacks of items. A most remarkable container!
It is a popular myth that NetHack characters do not wear pants. However, #sitting on a cockatrice corpse does not turn you to stone, so clearly the hero is wearing some form of pants, trousers or boxer shorts. Veteran roleplayers of TSR's Dungeons and Dragons are familiar with indestructible underwear that is impossible to remove. This tidbit does make them feel right at home in the dungeons of Nethack...until their first encounter with a Foocubus, of course.