By "jailbreaking" your iPad or iPad 2, you can get tweaks, themes, apps and mods that are not official or endorsed in any way by Apple. Jailbreaking has some benefits, and many of the current features of the iPad derive from jailbreak tweaks. The downside of jailbreaking is, if you dont know what you're doing, it can be very dangerous and ruin your device. Some jailbreak tweaks are also illegal. So YES you can mod your iPad if it is jailbroken.
there Is a thing called iExplorer and it's a non jailbreak way it install the mods but the rest I don't know
mods, mods, mods
moddb.com is good for mods. It has mount and blade mods and mods for virtually every other game.
you can get minecraft mods and textures off the minecraft mods website.
you can easily get mods from planetminecraft
The Mods was created in 1964.
look what ever game you want and add the word mods to the end on google. e.g oblivion mods, GTA mods
The easiest way to explain what the mods were is to watch the film Quadrophenia 1960s Mods & Rockers film
All mods are 'legal'.
Marvel mods
That depends on what mods you're talking about.
Get all the mods!