In terms of relational databases is a Relvar the equivalent to a Schema?

I've been reading up on relational databases and the term Relvar and schema keeps coming up. From my understanding:

A relvar is a variable holding a relation. 

A schema is a logical definition of a table. 

so I tried to imagine this in programming terms and I came up with this:

Relvar a = [Table 1 - Attributes a,b,c etc etc]
Schema b = [Table 1 - Attributes a,b,c...]

Is there any real difference?