Roll20. is a online platform to play RPGs online if you don't have friends or just need the that vidya feeling to your Pen and paper games. This particular combination allows for people to jump into any game that tickles their fancy or make a game they feel like running but lack an FLGS to run from or can't be arsed to drive.
- Recorded Dice Rolls. This allows you to avoid roll-fudging with physical die. If you really need the experience, you can even digitally roll them yourself.
- Macros and API so you don't need to do all the math for rolls.
- Access to the SRDs for certain rulesets.
- The ability to join any game you want, or open a game for people to run.
- An integrated forum for communications, which is infinitely easier than IRC, but maybe not compared to Discord or Skype.
- The whole thing is usable, but feels clunky and amateurish. As a GM, expect to have troubles categorizing and sorting your assets (such as tokens) for example.
- It runs like absolute shit on phones and tablets, if at all. Getting a paid subscription might make it a bit more bearable, but you're still hamstrung by the screen dimensions.
- Laughable native voice and video chatting, just in case you like seeing other neckbeards, but forgot/have crippling fears about using better services like Skype or Discord.
- Unless you're running a popular game like Dungeons & Dragons or Pathfinder, expect the list of available games to shrink considerably. You might not even be able to see any games running. To put this in perspective, in the last quarter of 2017, there where 49,265 active games of Dungeons & Dragons 5th Edition, compared to only 9856 active games of Pathfinder, dwarfing all other systems activity in comparison .
- Paid GMing, which is its own barrel of skub. That's right, you can have people actually pay you to GM for their amusement. Oftentimes, prepare to be stuck in the infinite morass of 5E.
- Some character sheets, especially those for less-played games, are just intolerable. Unless you know API or know someone who knows API, expect to be begging a lot for a better sheet. Note that you need a subscription to create your own character sheet, and that the API has some shortcomings (for instance, the choice of font is abysmal, creating tabs is a clunky process relying on CSS tricks, etc.).
- Dynamic Lighting, while cool sounding in purpose, is finicky to work with. This is especially the case when dealing with directed light. Fog Of War suffers similarly.