The Form S-3 is a simplified security registration form. It allows an entity to incorporate a large amount of information by reference, resulting in an abbreviated filing of information with the Securities and Exchange Commission to register securities. An entity using the Form S-3 can incorporate in it by reference information already filed in its Form 10-K, subsequent quarterly Form 10-Q reports, and Form 8-K reports. However, the Form S-3 can only be used by those public companies meeting certain requirements, which tends to restrict its use to larger entities.
An entity not able to use the Form S-3 generally uses the larger Form S-1 instead.