OK, your further information does not really help.
First Post: I am selling video's on the Internet and would like to know if I word my description of the product to say the product is not a copy will I still be going against someones copyright?
Second Post: I have some VHS exercise tapes and I make copy's and sell them for reduced prices.
If Post 2 is true and you do not own the right to copy and distribute the tapes in the first instance, then what you are doing is pirating and counterfeiting, which is highly illegal.
If Post 1 is true and you are selling copies, with permission to copy, failure to label the tapes as copies is misleading and false advertising. Your public does not know it is getting a copy of a copy, that is why it is false and misleading.
Your posts do not contain enough information to answer your questions as the permission to copy issue is important. You really should talk to an attorney because it sounds like you could be getting yourself into hot water, based at least on what we have here.
This is not intended to be legal advice. Rather, it is general information. We have no attorney client relationship you really should contact an attorney for specific advice.