I'm new to pbp games and I have only played 3.5/pathfinder at all. I've noticed most games here are for 5e and I'm itching to play so I'm eager to learn. What are the main differences between 5e and what I'm used to? Someone please help me in my conversion.
If your DM uses Feats and Multi-classing you'll hardly notice the difference. You have far fewer choices than 3.5/PF, aside from that, 5e should be very familiar. If you're familiar with 3.5 or earlier versions of D&D, you can prettymuch just sit down and start playing 5e with little trouble. The spellcasting mechanics take a few moments to wrap your head around - you prepare a certain number of spells like a Wizard, but not in the usual spell-level-based slots just a list of so many prepared spells based on caster stat and level, instead you expend your slots to spontaneously cast any of the spells you have prepared, like a Sorcerer.
Instead of a lot of fiddly modifiers to rolls, you usually get Advantage (roll 2d20, take the higher) or Disadvantage (same, take the lower) assigned by the DM.
If you're not used to pre-3e D&D, you may be taken aback at the way the game depends on DM rulings for everything, rather than having an explicit RAW and an expectation the DM will stick to it, or have equally explicit house rules up front if he intends to deviate from RAW.
Aside from that, it's lots of little differences, each of which might trip you up once. Kinda like going from 3.0 to 3.5 to Pathfinder, except that some of the differences are more like a step back towards 2e.