Option Pending is when you have certain days to inspect a house, most of the time is 10 days, after that you change your listing to pending if the buyer doesn't cancel.
Go to your home page in Matrix and you will find the definitions for all of the listing status's. It is listed in the "External Links" box. By default you should see this section if you have not removed it. Mine is on the lower right but they can be moved around to suit your needs.
Option pending and pending both mean that the property is under contract with a buyer. The difference between the two is that option pending means that the buyer has an unrestricted right to withdraw from the contract within a certain number of days, whereas pending means that option period has expired or the buyer did not negotiate one. I hope this helps!
See the definitions of these by the MLS below. Option Pending: "Listings that are under contract and the seller and buyer have agreed to use the “Termination Option” in paragraph 23 of the standard TREC contract" Pending Continue to Show "Used for listings currently under contract but are still available to show. Listings having a contract with a contingency and taking back-up offers should be Pending Continue to Show" Pending "Used for listings under contact and are no longer available to show."