Wikipedia's definition of "webisode" is basically just episodes of webseries. And while it can be used that way, that's not generally how I think of the term. (TV Tropes seems to get it, though.) Sometimes a TV show (or movie) will have bonus "webisodes" you can watch online, which are generally not more than a few minutes in length, so they're also sometimes called "minisodes." (There may also be other names for them, like "mobisodes" that are released via mobile phones instead of or in addition to the web. And some shows may give their webisodes cute terms based on the show's title or some element of the plot.) They may be one-shots, or part of a miniseries. Some are canonical to the series, and some aren't. I've seen several such things, over the years, and in this section, I'll be listing any of them that I can recall. I'm sure some shows I watch may have done webisodes without my being aware of it, some I may have been aware of but chose not to bother watching, and some I may have watched and later totally forgotten about.
stuff I've seen: