Great questions, Odyl.
First, I recommend you read the New Player’s Guide: [Guide] New + Returning Player's Guide (Season 20)
No matter what class you play, it has tons of really useful information.
“Builds” refer to specific combinations of skills and items, and are almost always dictacted by set bonuses. In reality, this means that sets dictate, to a very large degree, builds. For example, Barbs have 5 major builds, 1 each based on their four sets, and a fifth that combines two different sets.
Builds work in very specific ways, and if you tinker too much with a build, you can really weaken it–or in some cases, cripple it. In other words, builds require certain skills on the bar, certain items equipped, and certain items in the Cube, and you must use it all in a very specific way. Some builds, however, can be tweaked a little bit, and we call these “build variants.”
Builds that are competitive with each other in a given class are called “major builds.” Generally speaking, major builds are capable of clearing within +/- 10 Greater Rifts of one another. “Minor builds” are strong, but are generally used for lower GR clears or speed-farming Torments. Some builds are really only useful for speed-farming, and some are only useful for pushing GRs.
Builds can also be put together with the Legacy of Nightmares ring set, or the upcoming Legacy of Dreams gem. These items can, depending on class, dictate various major and minor builds, and we refer to these with the prefixes “LoN” or “LoD” (LoN HOTA, for example, was a popular Barb build last Season).
“Rolls” refer to the traits on an item. For example, you might find a helmet with:
- 500 Strength
- 255 Vitality
- 6% Critical Hit Chance
Each of these are rolls. If you take the helm to the Mystic, you can “enchant” or “re-roll” one of these traits. If you’re collecting gear for a specific build, you’ll need it to have specific rolls. In most cases, we’re very restricted by what rolls a build needs, so you normally need an item to drop with most of the needed rolls so you can afford to re-roll something at the Mystic.
The term “roll” can be used interchangeably to decribe the RNG present in the game. Whenever a monster dies, the game “rolls” dice to see if an item drops. Then it rolls again to see what kind of item, what stats, etc.
Hope this helps. Let me know if you have questions.