In synthetic chemistry, protecting groups (also sometimes referred to as protective groups) are used to mask reactive functional groups, either to prevent them from being transformed by a given set of reaction conditions or to prevent them from interfering with a desired reaction.
Functional groups are usually described as being protected or deprotected, and protecting groups can be described as being installed, added, or put on and then as being removed or cleaved. (Note that these are not the only options.) Here are some typical examples of standard usage: