Hello Safaa
Syntax, put simply, is the grammatical arrangement of each element of a sentence. It's main concern is ensuring the coherence of your subject, verb and object, as well as the relationships that tie them together. Involving a logical sequence, it's the framework from which you build sentences correctly.
Language Without Syntax
Each word we use in our language has a meaning. A combination of words is a sentence. When we string words together to form a sentence, the goal is for the complete statement to relay a specific message. How these words are arranged and presented is usually dictated by syntax. The reader, who looks at these arranged words, uses syntax to determine what it means as well.
Without the structure of a syntax, there is no point in putting words together to form a sentence - they would not make any sense anyway.