Role-playing is the act of taking on a fictional role in a fictional plot, often on a forum specially designed for this activity, though, role-playing may also be done over instant message clients, chat rooms, e-mail, "pen and paper", and live play. Role-plays that involve multiple users and textual methods can be compared to collaborative, interactive books, while role-plays involving live-play can be compared to stage acting. Role-playing is considered a form of entertainment.
Post-by-post is a term used to describe a role-play that uses such a system. A post-by-post role-play is a role-play that progresses little by little via individual text-based posts made by different people. People interact this way by adding snippets of story and dialogue to the role-play, each person making their own contribution and moving the role-play along using their own characters and non-playable characters. This kind of role-play ends when the host or the group decides that it should, or when no one continues to role-play.
Forums and Chat Rooms
Role-plays done via forums and chat rooms are usually group role-plays with more than two participants. These can range from a few people to a gross amount. When role-plays get very large, there is often confusion as to how the plot is progressing and who is interacting with who, which is a problem that can be easily solved with quoting functions and out-of-character comments that clearly state who the person is interacting with in the post.
Instant Message Clients and E-mail
Role-plays done via instant message clients and e-mail are usually one-on-one role-plays, where only two people interact together instead of a group. These can be fairly simple or even more elaborate than some group role-plays. Role-plays of this nature are often assumed to be sexual due to the privacy involved, though, they often lack any sort of sexual content.
Pen and Paper
When people think of "pen and paper" role-plays, Dungeons and Dragons is usually what comes to mind, however, there are many other kinds of table-top role-playing games. These role-plays can have very simple to very complex rules, and can have little to huge amounts of pre-construction for the setting and characters. Some table-top role-plays use figurines or cut-outs to aid in visualization, though, many people often ignore these extras.
Role-playing in a live setting is a various field. It can consist of as little as one person to many people. Often times when people think of live-play, they either envision pretend medieval warriors duking it out or a married couple locked in the bedroom while donning leather outfits.