This is the easiest thing to understand — it’s the same animal in both languages. It filters out result sets/subgraphs. Not all predicates have an equivalent in the other language, but the concept is the same.
SELECT * FROM "Person" WHERE "Person".age > 35 AND "Person".hair = 'blonde'
START person=node:Person('name: *') WHERE person.age > 35 AND person.hair = 'blonde' RETURN person