in addition to the default dimension the player starts in (called the "overworld"), there are also two other dimensions in minecraft - the nether and the end. both of these can be accessed with special portals. the player can make nether portals using obsidian and flint and steel, but end portals have to be found in strongholds. while it is not necessary to go to these dimensions, they have lots of different items and enemies which can not be found in the overworld. the ender dragon can only be fought in the end. after that, the player has a choice of going back to the overworld or to go to the end islands to find an end city and get an elytra.