Why are some colleges called a 'School of X' while others are a 'College of X'?

Why are some colleges called a 'School of X' while others are a 'College of X'?

In the US, you would have a School of Architecture as a part of the University. School of Engineering, School of Business, etc - all part of the University. For example, there is a School of Law at the University of Virginia.
In certain other countries, when it talks about a school, it refers to the standard of education you are legally required to take. A college is where someone goes to achieve a slightly higher, more specified level of education, For example, As or A2 levels, this is often attached to a high school, and a University is where you can go to get a degree in something. Also, if it is a school for adults as such, a school will teach you how to do something, whilst a college or university will give you a diploma.