Bomb

Bombs are staple items in the Legend of Zelda series, premiering in the first game and recurring in almost every game since. Needless to say, they are used to create explosions; a few seconds after they are used, they will flash red and explode in a puff of smoke. Bombs have many different functions, such as blowing up rocks or walls, defeating Dodongos, or damaging other enemies (or even Link himself, if he’s near the bomb when it goes off). Given these functions, bombs have been a staple of secret-finding, and an excellent combination of a tool and a weapon. In The Legend of Zelda, they appeared as blue balls with a white fuse coming out of them, and they kept this design until Twilight Princess, in which they were made black with a grey paper wrapping, keeping with the more realistic artistic approach in the game.

Bombs are usually found relatively early on in each game, and sometimes are kept inside a Bomb Bag. Generally, Link can only carry a set amount of bombs when he obtains them, but this amount can usually be upgraded throughout the game. Bombs can be obtained buying them from shops, obtaining them in pots or treasure chests, or from defeated enemies. Since A Link to the Past, they can be dropped, picked up, carried, and thrown. As soon as they touch the water, the fuse will turn out and they will not explode, with the obvious exception of water bombs. In the Wind Waker, they can also be thrown with the King of Red Lions’ cannon. Additionally, in Link's Awakening and Twilight Princess, they can be combined with arrows to create bomb arrows.

Variations
Being one of the original and most used of the Legend of Zelda series items, there are many variations to the bomb, not only in appearance but also in function.

Super Bomb
The Super Bomb is a red and bigger version of the bomb found only in A Link to the Past. It can only be obtained from the Bomb Shop in the Dark World, and it's available for 100 rupees, after clearing both the Ice Palace and Misery Mire. Unlike other items, however, this giant bomb is not in Link's inventory, but rather it follows him around until he needs to use it. It is only required to gain access to the cursed Fat Fairy, who gives Link the Silver Arrows required to kill Ganon.

Bomb Flower
Bomb flowers are a special exploding fruit found in the mountains, and they work exactly the same as regular bombs. They are usually used when Link isn’t able yet to carry bombs on his own, but needs to make certain rocks or walls nearby explode.

Bombchu
Bombchus are special bombs that resemble a mouse. These bombs, when set, will go forward on their own, even crawling up walls if they crash with one. They seem to be based on the Real Bombchus from Termina.

Remote Bomb
This special kind of bomb has only appeared in The Minish Cap. In this game, regular bombs can be exchanged for the silver-colored remote bombs with Belari after getting the regular bombs and fusing Kinstones with Gentari, the Minish elder. After being set, these bombs will explode only when the button to which they are assigned is pressed again. Because of this, it is impossible to have two remote bombs out at a time. These functions can be positive or negative, depending on the situation, and so they can be exchanged back for regular bombs at any time with Belari. When Link has the remote bombs, he will obtain these items the same way as the regular bombs.

Water Bomb
Water bombs are special bombs, found only in Twilight Princess, that are able to explode underwater. They appear as black balls covered in a fish-like wrapping, appearing as if they were being eaten by the fish. These bombs allow Link to blow up boulders underwater that normal bombs would normally defuse once reached. They are essential items found and required to complete the Lakebed Temple. To use them while underwater, Link has to have his Iron Boots on. Other than that, they work exactly the same as regular bombs, even on land. However, they are more expensive than regular bombs, so it is not recommended to use them when it's not necessary. They seem to be based on, or similar to, Bombfish, since when caught with a Fishing Rod, these fish can be kept as Water Bombs.

Image taken from Zelda Elements

Bombling
Bomblings are special bombs found in Twilight Princess. They are similar to the Bombchu, except they won’t crawl up walls, but rather will explode whenever they crash into something.