Meaning – The term option set, refers to a set of functions that may be supported by products that implement a particular architecture. A product may support any number of option sets or none. For each option set supported, all functions in that set are supported.
An option set is a type of field that can be included in an entity. It defines a set of options. When an option set is displayed in a form it uses a drop-down list control. When displayed in Advanced Find it uses a picklist control. Sometimes option sets are called picklists by developers.
Example of usage – “Global options sets are used to set fields when there are numerous fields that use the same set of options. Before you can add a global option set to an entity, it must be created first.”