A GSA is a security interest over a company or an individual.  

This security is perfected when it is registered on the publicly view-able Personal Property Security Register. 

It will accompany a loan agreement and allow the lender to take control of the asset which the GSA is registered over.  In the case of a company this would be the appointment of a receiver.

A company may have several GSA's registered over it but the first GSA holder takes priority in enforcement and collection.