Minecraft (Pocket Edition)
The above is an image of a Bed, which is how new Spawn Points are set.
There are two types of Spawn Points in Minecraft. First is the Original Spawn Point, the location you appear when you begin a new game of Minecraft. A Compass will always point to this place.
The second type of Spawn Point is one that is reset every time you sleep in a Bed. This type of Spawn Point is important because when your character dies and you choose to Respawn this is your new point of entry into the game.
For example, if you place your Bed and sleep outside a cave but then fall into lava while caving underground you will Respawn outside where you last slept.
The above image illustrates the Respawn option.
Usage / Purpose
Choosing your secondary Spawn Point is important, especially when adventuring or journeying long distances.
Beds are also active in Creative Mode (as of release 0.10.0) and will allow the player to skip through the night just as in Survival Mode.