Playlists are a convenient mechanism for specifying a sequence of macros to play along with the number of times that each macro should repeat.
Take for example a common use case that consists of signing into a website, performing a search or query, and then iterating over the results to extract the data. Since only a portion of this sequence needs to be repeated (iterating over each result), the solution is to split this task into multiple macros and play them back using a playlist.
Playlists use JSON syntax and can be specified directly on the command line using the -playlist switch, or they can be saved to a .json file. JSON files can also be specified on the command line, or you can play them directly in the browser just like you would any other macro file.
Playlist files can be created with any text editor including the iMacros Editor, which provides a playlist generator for easily constructing your playlists.