1) She is a beautiful girl.
In this sentence ‘beautiful’ is an adjective,

Now see this sentence.

2) She is a girl of great beauty.
In this sentence ‘of great beauty’ is an adjective phrase.(Phrase is a group of words depicting one meaning).

Let us see this sentence.

3) She is a girl who is beautiful.
In this sentence ‘who is beautiful’ is a Clause. (A Clause is a group of words with a subject and a predicate.)

Look at the 3^rd sentence carefully. She is a girl can stand alone but who is beautiful cannot stand alone. It needs the support of the first part of the sentence.

Now we shall divide this sentence into 2 parts. She is a girl /who is beautiful. The second part of the sentence needs the support of the first part.

The result is;

She is a girl—Main Clause

Who is beautiful—Subordinate  Clause.

Now this subordinate clause  says something more about the noun ‘girl’ in the Main Clause.
A word that says something more about a noun is an Adjective and so a clause that says something more is known as an Adjective Clause.

Some more examples of sentences with this Clause;
a)     The man who is fat is my grandfather.
b)    Raja likes movies that are directed by Manirathnam.
c)     The stone which shines the most is the diamond.

I hope you have tried to understand the concept of the Clause Analysis.

We shall see all the types of Clauses one by one.

Try to analyse the sentences given into Main Clause and Subordinate Clause.

BUT WHY DO PEOPLE IGNORE GRAMMAR?
Usually we hear people saying, “It is of no use to go through a thorough grounding of the rules of grammar”. Particularly those who have an excellent command over a language would say so and tell others not to waste their time bothering much about this aspect of language. Interestingly, they never pay attention to the fact that they have those skills already otherwise it would not have been possible for them to use the language as skillfully as they do. Thus, it is in no way justified to deny similar skills to those who face problems in using the English language.

WHAT IS THE RIGHT WAY TO LEARN GRAMMAR?
Learning grammar may sometimes seem tedious to most beginners. But if it is taught in a creative as well as an interesting manner the same proves to be one of the most exploring experiences. The learning of English grammar through the typical traditional classroom teaching is most discouraging. The teacher must make the students walk through the concepts of grammar, dance to the tune of its rules and play with its functions in the most creative and fun-loving ways. It is well said by John Didion

“GRAMMAR IS THE PIANO I PLAY BY EAR. ALL I KNOW ABOUT GRAMMAR IS ITS POWER”
It is ideal for the novice in English language to start with knowing the Alphabet and Numerals leading to a step by step thorough
grounding of BASIC GRAMMAR. He must work hard to learn the functions of different parts of speech i.e. noun, pronoun, adjective, verb, adverb, preposition, conjunction, and interjection. Once the beginner becomes familiar with different parts of speech he\she is ready to grasp the general vocabulary of daily use. Then, it’s time to take him\her to an advance stage of Grammar i.e. to learn about Inflection.

INFLECTION is defined as the change in the form of a word in order to express a grammatical relationship.
“An alteration of the form of a word by the addition of an affix as in English dogs from dog, or by changing the form of a base, as in English spoke from speak, that indicates grammatical features such as number, person, mood or tense.