All wow chapters include the ability to play one of the six core professions—Warrior, Ranger, Elementalist, Necromancer, Mesmer, and Monk. The first chapter, Prophecies, allows only these six professions to be created about wow gold; but each new chapter has introduced two new professions. In Factions, players could create an Assassin or a Ritualist, while Nightfall players can make a Dervish or a Paragon about wow gold.
A player who owns only Nightfall does not have access to the Assassin or Ritualist professions for their characters, while a player who owns only Factions can not make a Dervish or Paragon. However, players who own multiple chapters have access to all professions, and can use a character from one chapter in the missions of another. For example, someone who owns all three chapters can create an Assassin in the Factions continent, and then transport their Assassin to the Nightfall or Prophecies continents.
I only want to buy one chapter. Which one should I get? There are many factors to consider here. I have put together a small table for reference, with each line explained in detail below.
If this is your first experience with wow, the learning curve can greatly affect your opinion of the overall game. The original release, Prophecies, is widely considered to have the smoothest learning curve. Due to factors discussed a bit lower on the screen, Prophecies eases players into new aspects of the game much more slowly than the later chapters.
Factions is widely considered to have the sharpest learning curve, oriented more towards experienced players who played Prophecies than to new players about wow gold. Nightfall falls somewhere in between the two, but is much closer to the slower pace of Prophecies than to Factions haste about wow gold.