You can find many zones which have rifts you could adventure through in your pursuit to level 50. A rift is one way portal that takes you from your home territory to the enemy's. Every rift appears randomly at set locations throughout the game world. They have maximum capacities which means once a certain number of persons go through them they will close.
Using rifts is a popular way when people are getting to a higher level. For people who love to PvP, it really is a thrill being in enemy territory. Just knowing that the enemy could be at the next corner or coming up behind you at any time. Some Rifts are for higher level players and take you into areas much higher than you might be, while others do just the opposite. there are "safe" zones for the faction you choose. For Elyos you can find refuge in Theobomos. And for Asmodians you can find the refuge in Brusthronin. You can take a break in the places.
Rifting can be very fun and rewarding experience and taken with a grain of salt. Having an open PvP experience does make it seem more realistic for people who are looking at it from a practical stand point.