When exporting captions, users have the option to choose both the file format and frame input. The file format determines the type of file that the captions will be saved as, such as SRT, VTT, or SSA. The frame input refers to the starting timecode for the captions, and users can choose from different frame rates depending on their specific project needs. By selecting the appropriate file format and frame input, users can ensure that the exported captions are compatible with their desired video player or platform.