How to use more Advanced Commands!

/summon /summon is used to summon any entity, such as a zombie or a dropped item. Type into the chat:"/summon Villager". This will summon a random villager right at your feet. Typing:"/summon " and then pressing tab will show all the things you can summon; a lot of things!

Note: Giant is a giant zombie, and summoning Item Frames isn't working currently, as of 1.8.

You can also summon entities at specified coordinates. Type into the chat:"/summon Villager ~ ~2 ~". This will summon a Villager 2 blocks above your head. If your going to enter at a specified location, type:"/summon Entity x y z" while replacing Entity with your entity of choice, and x y and z with your specific coordinates.

Note: You cannot summon an entity outside loaded chunks, and ~ can be used as any coordinate.

Data tags would be the next thing, but it's all crazy complicated. Just to see what it can do, type:"/summon Villager ~ ~ ~ {Profession:2}", and you'll get a purple Villager! There are loads of YouTube videos which show how you can use many of these NBT tags, such as changing speed, health, armor, and dropped items!