An image sequence is a series of sequentially numbered files, traditionally the result of scanning film stock at high resolution to produce a digital intermediate. Each file contains the digital scan of an individual frame. Common formats include Cineon, DPX and Tiff. The file type is usually indicated by its extension.
In contrast, container formats, also called “wrapper” formats, can contain image sequences (commonly called streams or essences) and audio, compressed using a variety of compression algorithms (codecs) into a single file. Container formats do not impose specific video or audio codecs upon the media they contain. Rather, a container format defines only how the video, audio and other data is stored within the container itself. Unlike image sequences, it is not possible to tell by looking at the extension what kind of video or audio is inside a container format.