@fishbuddy: PoE has four flavors: Level 28, 32, 34, and 35. Level 28 has random modifiers for rounds 2, 3, 4 and 5 and a random boss at round 5 and supports matchmaking. So you can go in solo and the game will pair you up with other Guardians.
Levels 32 and higher require pre-made Fireteams and feature set rounds, modifiers and bosses. But you'll get drops enabling you to make purchases from Variks, the PoE vendor, as well as Etheric Light, the item needed to boost non-House of Wolves Legendary gear to top-end Year 1 stats.