Parking a call is similar to placing a call on hold, except that it allows any other extension to pick up the call by dialing the parking lot extension. A parking lot is similar to a line key on a traditional phone system.
Additionally, depending on the phone model you are using, we may have programmed a few keys as "Parking Spaces". These keys can be used to place a call in Park, and will show red if a call is on hold and green if the parking space is free. The process for placing a call in one of these parking spaces is the same as above, except rather than dial the extension (ex. *300) you would press the appropriate parking key after hitting transfer.