Planemike,
The technical word you're looking for is buffering.
In an ideal world, what SHOULD happen is that your web browser reads a little bit of the film content into memory (i.e. reads it into a memory buffer, hence buffering). The buffer then gives your browser a "head start", so it can start playback on the video whilst loading the remainder progressively in the background, either entirely or as a rolling buffer.
BUT.... if you have a slow internet connection, or the server at the other end is having problems, then you may well encounter buffering problems.
Videos play at 25-30 frames per second, and HD videos have large frame sizes .... so you can imagine, it doesn't take long for a browser to get through 30 frames and your internet connection can't keep up. Hence the video stops, because its eaten up all the buffer and has not been able to pull more data.
So, what to do :
(1) Make sure your browser and all plugins (e.g. Adobe Flash) are fully up to date
(2) Check your internet connection, talk to your ISP if necessary
(3) On sites like EweToob that offer the option, switch to a lower quality stream (i.e don't use HD feeds if your internet connection is obviously not up to the job).
(4) In the particular case of EweToob, their default streaming format is Adobe Flash. You can try switching EweToob to HTML5 mode and see if that helps. Unlikely to be the cause of buffering, but if you're getting desperate for things to try !!!