The relational algebra consists of:

a set of eight operators (which ones?) and

a relational assignment operation

The relational assignment operation allows us to assign a name to the result of a relational expression, for example if we take the product of two relations A and B, then:

C ← A X B shows that the result of the operation A X B is assigned to a new relation called C.

In other words, what we see is a named expression of the relational algebra, also called a view. A view has no stored physical data, it is a virtual relation, expressed in term of one or more base relations. Views, in turn, can be used to write nested expressions involving base relations or other views.