Fortune is an Enchantment added by Vanilla Minecraft. It regularly applies to Pickaxes. When in effect, it makes "gem" ores such as Coal or Diamond that drop their mineral when normally and successfully mined drop more than usual. This should be one of the first enchantments used on a high-tier pickaxe in order to get the most out of ores found.
In Tinkers' Construct mod, you can obtain this enchantment on tool made using it by adding Lapis Lazuli as a modifier to it.
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You can use a looting enchanted tool to break fully grown crops and get more items. This also applies to grass which means if you want seeds, you can use a looting enchanted tool to increase your chances of getting seeds.
You can't use a looting tool to get more books from bookshelfs. It will always give you 3 books.