Meaning of SPARQL operator ';'

What does ';' operator in WHERE clause means in SPARQL?

For example:

SELECT ?x ?y
WHERE { ?z foaf:name ?x ; :surname ?y }

What the ; operator means here? Is like a logical and that means this part

?z foaf:

goes before :surname again?

It's not a SPARQL operator, but rather part of the syntax for triple patterns in SPARQL. The full specification is in section 4.2 Syntax for Triples from the SPARQL spec. Subsection 4.2.1 Predicate-Object Lists describes the ; notation:

Triple patterns with a common subject can be written so that the subject is only written once and is used for more than one triple pattern by employing the ";" notation.
?x  foaf:name  ?name ;
    foaf:mbox  ?mbox .
This is the same as writing the triple patterns:
?x  foaf:name  ?name .
?x  foaf:mbox  ?mbox .

You might also be interested in subsection 4.2.2 Object Lists:

If triple patterns share both subject and predicate, the objects may be separated by ",".
?x foaf:nick  "Alice" , "Alice_" .
is the same as writing the triple patterns:
?x  foaf:nick  "Alice" .
?x  foaf:nick  "Alice_" .
Object lists can be combined with predicate-object lists:
?x  foaf:name ?name ; foaf:nick  "Alice" , "Alice_" .
is equivalent to:
?x  foaf:name  ?name .
?x  foaf:nick  "Alice" .
?x  foaf:nick "Alice_" .

The same syntax is used in Turtle and N3 serializations of RDF. See 2.3 Abbreviating groups of triples for Turtle, which says

The , symbol may be used to repeat the subject and predicate of triples that only differ in the object RDF term. … The ; symbol may be used to repeat the subject of of triples that vary only in predicate and object RDF terms.

and for N3, see the Semantics section, which says: