AVI is one of most popular video standards in internet and you would expect every platform or device to support these files. But on iPad you may fail to play them due to compatibility issues. As we know iPad supports MP4 format. You may find an app that allows playing avi files on ipad, but these apps usually have limited number of supported video formats like H.264. So if you want to watch avi video it is recommended to convert it in to proper format.
You can find lots of video converters on internet that does this job pretty well. One of these is Video Converter Ultimate from Aimersoft.com. They provide free version of video converter that runs on Windows and MAC. It supports multiple video formats including WMV, AVI, MP4, MKV, MOV, 3D video and HD video. With Video Converter Ultimate converted video plays on majority devices like iPhone, iPad, mobile phones and other platforms.
Video converter Ultimate is not only able to convert videos from one format to another but also allows editing them by trimming, cropping, tweaking visual effects or adding watermarks. There is also possibility to merge multiple videos in to single file.