Promotional recording

A promotional recording (or promo), is an audio or video recording that is released for free. They are released to promote a song that will be released through an album. Promos are sent to broadcasters, such as music radios, television stations, tastemakers, DJs, and music journalists. Recording labels perform this for their artist(s) to achieve airplay, positive reviews, and other exposure for fame. 
Promos are often released in plain packaging. This means that a artwork or text may not appear on the cover. Most promos are marked with "Licensed for promotional use only. Sale is prohibited." In some cases, promos may ask the owner to return the promo back to the record label. However, it is not against the law to sell promotional recordings. There has been recalls of promos, but this is rare and not forced by recording labels.
Because promos are released in smaller quantities than CD singles, they are sometimes considered a collectors item. They are never released in record stores. Promotional recordings, in terms of airplay, can chart on the US Hot 100 Airplay and not the "Billboard" Hot 100 chart. This is because, the promotional recordings are not released physically.