1) What is a sentence

A sentence is a group of words, which makes complete sense. It can stand on its own without needing any additional words to complete its meaning.

I'm twenty years old.                    Your hand bag is on the table.     

 
a. A sentence can be broken up into two parts: The Subject & The Predicate.

The rain fell heavily

The Subject                           &                          The Predicate
The rain                                                Fell heavily

A sentence containing one subject and one predicate is called a
Simple sentence.

Many sentences, consist of two or more groups of words, each of which has a subject and a predicate of its own.

Look at this example:

1. The weather was fine.

2. We walked everyday.

3. The weather was fine and we walked everyday.

Sentence (1)  Is a simple sentence.       

Sentence (2)  Is a simple sentence.

The two simple sentences are linked by the conjunction "and" to form sentence (3) which contains two subjects and two predicates.

The weather was fine and we walked everyday.