MTS file is a High-definition MPEG Transport Stream video format, commonly called "AVCHD;" used by Sony, Panasonic, and other HD camcorders; based on the MPEG-2 transport stream and supports 720p and 1080i HD video formats.
MTS is a file-based format and does not usemagnetic tape. Instead, video can be recorded onto DVD discs, hard disk drives, non-removable solid-state memory and removable flash memory such as Secure Digital and Memory Stickcards.
One of the common problems many AVCHD camcorder users often meet is that they always failed to import their .mts footages to FCP/iMovie/AviD for post editing. Why? That's simply because these video editors do not natively support MTS/M2TS format. To get rid of this problem, you need to, for example, connect your camera to your Mac and then use "Import from camera" command to import the AVCHD files to FCP/iMovie. If you only have the files in .mts extention, you have to convert MTS to FCP accepted formats like ProRes 422 in advance.