The Media Library is an area in the Whooshkaa dashboard where you can store the media files that you plan to reuse. These files may be audio, video or image files.
In general, you would store only the files that you plan to reuse in your Media Library. Single use audio -- such as episode audio, for example -- is probably best kept out of the Media Library. Audio or imagery that you plan on re-using (e.g. intros or ad creative, reusable episode cover art) is a great use case for the Media Library.
Every tenancy has a limit to how much content may be stored, according to its plan. Storage limits are calculated in (decimal) bytes where 1 KB is calculated as 1,000 bytes, 1MB is 1,000 KB (i.e. 1,000 times greater), 1GB is 1,000 MB and so on. Please note that storage limits are expressed in gigabytes, not to be confused with gibibytes.