Game play is what the player interacts with and experiences during the game. It's basically what the player does whilst playing. Game play has developed from video games to the more traditional type of game forms.
Atari, Nintendo, EA games/Sports, on-line systems are all leading and popular companies in game design. Since computer games started they have been producing great games. Game design has evolved a lot since the beginning. The programmer was often designing game play, Atari often did this with many of their titles. Beforehand one person could create an entire game alone but since games became more complex to make and create there was now a new position of 'level designer'. Because of this more people were employed to create the vast design of a game.
Now they are many jobs that are there to create a level in a game. Level designers or map designers individually construct the game play. Not all games have the same design patterns. Some games may have a 2d base some may have 3d.
Whats important to me when i play games is that the game itself has to be interesting. Like World of warcraft, the maps are simple for me to follow, theres plenty to do in terms of quests and interaction with creatures and other players. I find that the design of the game and the game play itself to be most important, because without them the game is pretty much boring.