bigWig - The bigWig format is best for displaying continuous value plot data, such as read depths from short read sequencing projects or levels of conservation observed in a multiple-species alignment. A bigWig file contains a list of chromosome segments, each of which is associated with a floating point value. When graphed, the segments may appear as a big "wiggle". Although each bigWig file can contain only a single value for any given base, bigWig tracks are often combined into "container multiWig" or "compositeTrack on" tagged tracks. For information on creating and configuring bigWig tracks, see the bigWig Track Format help page.
bigBed - BigBed files are binary indexed versions of Browser Extensible Data (BED) files. BED format is useful for associating a name and (optionally) a color and a score with one or more related regions on the same chromosome, such as all the exons of a gene. See the bigBed Track Format help page for information on creating and configuring bigBed tracks.