AVCHD is abbreviated for "Advanced Video Codec High Definition", a format for the recording and playback of high definition video.
M2TS is a format container for multiplexing audio, video and other streams based on the MPEG-2 encoding scheme. It is commonly used for high definition video on Blu-ray Disc and AVCHD.

Camcorders that creat AVCHD.m2ts files:
JVC - GZ-X900 (SD/SDHC card), GZ-HD320 (120 GB HDD, MicroSD), GZ-HD30/GZ-HD40(HDD, MicroSDHC card) etc.
Canon - HF S11 (SDHC), HF S100 (SDHC), HF20/HF200 (SDHC), HG20/HG21 (HDD, SDHC), HF11/HG21 etc.
Sony - HDR-CX500E/520E, HDR-XR100 (HDD), HDR-CX12, HDR-SR12, HDR-CX7, HDR-SR8 etc.
Panasonic - AG-HMC40 (SDHC), HDC-TM350, HDC-TM30/SD10, DMC-GH1 (SDHC; AVCHD), HDC-SD200 (SDHC) etc.
Now let's see how to convert .m2ts to iPad compatible MP4 format by using a 3rd party M2TS to iPad Converter which runs smoothly on Mac OS X.
Note: if you are using Windows and want to convert M2TS to iPad, you can refer to Video Converter Ultimate for Windows.
Launch Video Convertefor Mac, drag the video files directly onto the interface.

Click "Format" and choose "iPad Video (*.mp4)".

Click "Settings" Choose "H.264 Normal(MC)" and all parameters will be automatically set for h.264.

You can learn more: How to edit, crop, trim video files and capture pictures with Video Converter on Mac OS X?
After choosing the format, you just need to click Convert button to start the task.
Tips: Add $14 You can get a powerful all-in-one Video Converter + Video Editor+ DVD Ripper: Video Converter Pro for Mac.