Pokemon GO requires the player to hatch eggs by incubating them and then walking a certain distance. The distance that is required for each of the egg usually depends on the rarity of the Pokemon. 2 KM eggs will usually result in a common type while 10 KM eggs are most certainly going to contain a rare type of Pokemon
Egg hatching can also be used as a way to farm experience points by using it in combination with a Lucky egg. You can refer to this level up and rewards guide to determine the experience points required for the next level up in Pokemon GO.
If you are interested in hatching eggs to locate some of the rare Pokemon, you can refer to the image below to determine which Pokemon can be hatched from the eggs.
There are a couple of trick to hatching eggs since it is not possible to cover such a distance on anything else other than on foot. Pokemon GO app can detect a high speed vehicle and counts it as a cheat for egg hatching. The best way here is to use a bike to travel around the map as this doesn’t count as a cheat for the game.
To hatch an egg, you will need to find an egg incubator which can be awarded on a level up or found at Pokestops. To use these Incubator, you need to head into ‘Eggs’ tab and then select the egg you want to incubate. A walking distance will be usually given for that egg and to count as walking, the app needs to be open at all times in order for the egg to hatch.
Pokemon GO is available now for the iOS and Android.