About multi-select attributes

If an attribute on your records can have more than one value, it is known as multi-select. For example, an attribute "Flavor" on wine records can have values "Apple" and "Apricot".

The schema for your records controls whether a standard attribute can have a single value, or multiple values. Attributes with multiple values can be of two types:

multi-select AND attributes (also referred to as multi-and)
multi-select OR attributes (also referred to as multi-or)

Respectively, refinements on such attributes are also known as multi-select refinements.