When is a sailboat the stand-on vessel?

A sailboat is considered the stand-on vessel when it is under sail and is being overtaken by another vessel, typically a powerboat. In this scenario, the sailboat has the right of way and must maintain its course and speed. Additionally, if the sailboat is on a port tack and encounters another sailboat on a starboard tack, the starboard-tack vessel is the stand-on vessel. The key principle is that the stand-on vessel should keep its course while the give-way vessel must take action to avoid a collision.