Adjective Clause is a subordinate clause which does the work of an adjective. That is, that group of words with subject and predicate gives more information about noun.
a. The student, who scored good marks, has been appreciated.
b. He tamed a dog, which is like a tiger.
In (a), ‘who scored good marks’ is a clause.
[ subject- who, predicate- scored good marks (verb- scored)]
It qualifies the noun ‘student’. So it is an Adjective Clause.
In (b), ‘which is like a tiger’ is a clause.
[Subject- which, predicate- is like a tiger (verb- is)]
It qualifies the noun ‘dog’. So it is an Adjective Clause.