Codec
This refers to the specific method of compressing the video file. Some of the above filetypes have a single codec, while others give you a choice. Some codecs are better at certain types of video than others.

Compression
Digital video requires a huge amount of data. Uncompressed video takes about 1.4 GB/min, far too much to deliver or even play. Digital compression uses various techniques to get acceptable image quality in a smaller package. The frame size or frame rate can be reduced, or redundant information discarded. Generally the more the file is compressed the lower the final quality will be.

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Data Rate
This refers to the amount of data required in a specific time. Sometimes the rate is given in kilobits per sec (Kbps) or megabits per second (Mbps), such as when talking about networks. Sometimes it's given in kilobytes per second (KBps) or megabytes per second (MBps), as when we say a CD can deliver 150 MB/sec. So it's important to be careful with our terms.

Frame Rate
This is the number of pictures in each second. Standard film uses 24 frames per second, or fps. Video uses 30 fps. Most web video uses much lower frame rates, to help limit the data rate. This can have a large impact on motion quality.

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Frame Size, Full Frame
This refers to the size of the picture. Usually it's compared with a standard display of 640x480, so "quarter screen" would be 320x240, half the width and half the height. Some web video reduces the frame size to 160x120.

Hyperlink
Some video can allow branching to web sites or other video, by providing a clickable hot spot within the picture.

Streaming
Until recently web video had to be downloaded completely before playing. Streaming video allows playback to start before the download is finished, giving the viewer a quicker gratification. Sometimes this means the video will pause to wait for more data to download.

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