FLV is a free container format created to deliver multimedia over the web using Adobe's Flash Player. The FLV multimedia container is the most common format used for embedding videos within websites.
FLV multimedia files contain a short header, but also interleaved video, audio, and metadata streams.
FLV editors will allow their users to modify the length of their videos, to quickly apply watermarks, to crop and cut movies.
Furthermore, these apps will also offer users the option to apply video effects and insert subtitles.