Confirms that the file includes subtitles , usually English since it's a foreign film. ROSASWEDDING: The shortened title of the film. Availability
If you're curious about what all those technical tags in the filename mean: Likely an internal database ID or release number. BR: Stands for Blu-ray , indicating the source of the video. 13781-BR1080p-SUBS-ROSASWEDDING.mp4
The resolution (1920x1080), meaning it's in Full High Definition. Confirms that the file includes subtitles , usually