A Boarder is a participant of the PPC community, so called because our primary community hub is the Board. Community members can also be called "PPCers," but usually aren't because that can apply to agents, too. It is important to note that Boarders are not agents. Boarders are real people; agents are fictional characters written by Boarders.
Some Boarders do have names that correspond with the names of their agents, such as the Trojanhorse. Agents that share a name with their author are often self-inserts, but not always—Agent Huinesoron, for instance, has little in common with Boarder Huinesoron (besides being an elf, of course), and even agents that start off as self-inserts tend to evolve away from the personality of their writer as time goes by.
Others, such as Tungsten Monk, have a completely different name and personality from any of their agents.
Still others do not have agents at all, but are there to provide support, mock badfic, and, according to the PPC Constitution, "natter endlessly about everything from our favourite canons to apple pie. Mmm, pie...".
While posts on the Board should be proofread before hitting "Post," typos still sometimes occur. Despite not exactly being canon characters, a misspelled Boarder's name will, in fact, produce a mini-Boarder.