All sentences make complete sense on their own, but not all sentences do the same kind of work.

There are basically four types of sentences. They can perform different functions:

Make statements.                                         Ask questions.      

Give commands.                                          Utter exclamations

 1. The first type of sentence is known as a statement sentence.  

The test was difficult.                That model has not ten gears.

 Affirmative (Positive) statement. Ali was ill.

Negative Statements. Ali was not ill.

2. The second type of sentence is known as a question sentence.  Positive Question.

Did you pass the examination? 

Are you Jordanian?

Negative Question.

Is Ali not coming with us?

Haven't you visited Jerusalem?