Caveat emptor is Latin for "let the buyer beware."
It is a conservative term that supports free enterprise rather than government regulation. It means that the terms of a trade or a contract are solely between the parties involved, and it is not the responsibity of a nanny state to intervene, in the alleged best interest of one party.
For example, in the United Kingdom the Food Standards Agency regulates what food can be sold, how it can be packaged, and so on. A pure application of caveat emptor would argue for the FSA's abolition, leaving it up to consumers to decide what food to buy, and trusting to producers' best interests (e.g. desire for repeat business) to incentivize them to produce food that is safe and of a suitable quality (see invisible hand). More moderate advocates of caveat emptor might argue for a minimal role for the FSA, perhaps ensuring that food is safe to eat but not intervening further with health-related regulations such as salt and fat content.