Weapons Mod

I want to start off by saying I'm new to this website and not sure if I'm in the right area. Now let's cut to the chase. I want to create some weapons such as an emerald sword. There's many things such as harvest level, efficiency, enchantability, and damage. For example, I know that the harvest levels determine what level of wood or iron or diamond is required to acquire this item.However it isn't a block. If I said 3 for diamond what does that do? It's not minable it's a sword. As for efficiency I understand it as how fast I want it to strike? I don't know. Enchantability, is completely confusing. I don't understand. What does each of these mean to each different type of items such as blocks, items, tools, weapons, etc. I'm really confused.