The NIST sets forth 4 types of media sanitization:
Disposal is the act of discarding media with no other sanitization considerations. In other words the media is not erased, degaussed, shredded or otherwise sanitized it is simply trashed.
Clearing is the act of overwriting not only the logical storage location of a file(s) (e.g., file allocation table) but also may include all addressable locations. Typically a software solution like Kroll Ontrack’s Erasure Software (http://tinyurl.com/7wlcm97) is used to accomplish this type of sanitization.
Purging information is a media sanitization process that protects the confidentiality of information against a laboratory attack. it should be noted that with newer drives, the classifications of purging and clearing have essentially merged. Purging also includes electromagnetic destruction (degaussing). The NIST also references use of the Secure Erase command for ATA drives, but this needs more research to confirm that it is as effective as a clearing by writing all sectors to a disk or degaussing.
Destryoing is the ultimate form of sanitization. The NIST references 5 types of destroying media. Disintegration, Incineration, Pulverization, Melting and Shredding.