The Sentence:-
Sentences are a group of words which make sense, are spoken together and convey an idea or a thought. When you want to develop English Speaking ability, in fact you are trying to develop your ability to make grammatically correct English sentences.

But let us first understand - What is a sentence?
An English sentence is a group of words with four characteristics:-
1. All sentences begin with a capital letter: A, B, C,….
2. All sentences end with a period (.) or an exclamation point (!) or a question mark (?)
3. A sentence contains at least one clause.
4. All sentences follow a standard word order.

Now let us see - What is a clause?
A clause is a group of words that contains a subject and a predicate. A clause tells us that someone or something (subject) is or was or does or did something (predicate). A subject is usually a noun or pronoun. A predicate always contains a verb. A predicate may also contain other things (adverb, object, complement etc.

A clause may be a sentence: for example : Mary sings.
A clause may also be a part of a sentence: Mary sings and Bill plays the guitar.

Some more examples of clauses:
George is a boy.
He loves to eat.
Pizza is not served at George's house.
Now let us consider - What is a predicate verb?
A predicate verb has the following three characteristics:
i) A predicate verb has a subject, usually a noun or a pronoun.
ii) A predicate verb has voice (active or passive).
iii) A predicate verb has tense (past / present / future) or a modal
For more information please visit this video on Sentences.