Apple iTunes is used for playing and organizing digital music and video files. The program is also an interface to manage the contents on Apple's popular iPod digital media players as well as the iPhone.

File format support
iTunes can currently read, write and convert between MP3, AIFF, WAV, MP4, AAC,mov and Apple Lossless. For some other formats, such as MKV, WMV, MOV, MPEG, 3GP, AVI,FLV , HD video(.ts, tp, trp, m2ts, mts) and DVD movie,  iTunes can't be supported them. If users want to watch them on their iPod or iPhone, they should use DVD/Video Converter to convert the files to iTunes compatible formats.

For Mac user, The following the guides tech you how to convert the files before transferring them to iTunes.
The Guide of DVD Ripper for Mac    The Guide of Video Converter for Mac

How to transfer files for iPod,iPhone using iTunes.

Step1.

Click My IPOD under the DEVICES, and select “Manually manage music and videos” option in the Summary window.

Step2.

Click File and select Add File to Library to locate your mp3 or mp4 files. Please see the picture. The added files will be automatically classified in the Music or Movies Category under LIBRARY.

Step3.

Click Music or Movies under LIBRARY, drag the music or movie from the library file list to My IPOD.

Then pull out your iPod or iPhone from computer, you can find the uploaded files in the movie list of your iPod (iPhone) and play them.

iPod related Tutorials - Convert Video and DVD to iPod and other iPod Resources

Next article:How to convert DVD movie to iPod Touch and iPod Nano?