I have been using the new BBCiPlayer for some downloads. They keep saying that it will have some problems because it is 'BETA'. What exactly does that mean?
It means it is still being tested, you the user are a guinea pig and they will not accept liability for any damage caused by used the beta version of their product.
The product may be unstable because it has not been tested enough to find and fix any 'bugs' and faults.
It's like a trial version that you and others are in a way testing for the manufacturer who'll gather the data on reliability, bugs, and general dislikes before releasing a (hopefully improved) final version.