Collateral is the term often used in the US to describe property which is pledged as security for the satisfaction of a debt. In this context, collateral is an additional security which is intended to ensure the performance of the principal obligation and which is forfeited in the event that the obligation is not performed.
In the UK, the term security is used. Property is provided “as security” but the property which is pledged is also called the security.
There are no differences in the meanings of the words, it is merely the fact that collateral is often used in the US and security is used in the UK.