Portals are gate ways that can form a network of teleporters that can be bought with crowns or found in the world, often in dungeons.
Orange teleporters bring you to a different server, or world. Blue teleporters are used to transport you to another teleporter. They are an easy way to move around within a world or server.
A teleporter cannot be placed within 50 blocks of other teleporters. Teleporters have a very small protection field and they can be bought with 40 crowns. (Note that orange teleporters can not be bought, only blue teleporters.)
Portals discovered in dungeons are often broken and cannot be used. However, they can be fixed with a click. Clicking on them again can allow you to access any other open portal. Blah blah blah blah Deepworld blah blah boring blah portals.