The DM/GM can be what makes or breaks a game. There's a lot of responsibility placed on their shoulders to make sure that the adventure goes along as smoothly as possible. You gotta come up with NPCs for the players to interact with. You've gotta create the dungeons. It's a lot of work. And a lot of gamers don't want to do it. Thankfully, there are ways to get around having to have a DM/GM for your game. Cactyys Totem Gaming has a new version with their Mythic rpg.
To play, you use their online game simulator. That will explain what the room is like that you're in and other such details. So basically, the online system takes the place of the DM/GM for your game. From there, it's like a regular rpg. You've got your PHB with your character all statted out and so forth. Since the game doesn't need a GM/DM, you can play solo or with groups up to 5.