The Discover Video standard for video files is H264 video encoding with AAC audio encoding contained in a .mp4 wrapper. In most cases, a .mov file is the same as .mp4, provided the .mov contains H264 compressed video with AAC audio.
There are two common issues that inexperienced users encounter:
1) Creating a video file that is intended for playback on their computer rather than streaming. The default condition for many video editing tools and consumer programs is to output the video at very high encoding rate, often in excess of 10 Mbps. While you can upload and stream such a file (provided it is H264/AAC), performance may be terrible because the file will be streamed at the encoded rate. A file encoded at 10 Mbps will use 10 Mbps of bandwidth for each viewer. It is unlikely to work well on the public Internet, and unlikely to work well on cellular-connected Smartphones and tablets.
Video files should usually be encoded at <1 Mbps, and at 640x480 for 4:3 or 640x360 for 16:9 aspect ratio. But it depends on the intended use, and many encoder configurations are possible.
2) Creating a video file that is not prepared for streaming. While most modern tools will properly create video files for streaming, it is possible to create files where the "MOV atom" is not properly positioned at the head of the file. The fast that a video plays locally on your computer does not mean it is a "good" file.