This drawing illustrates a short piece of the DNA helix and illustrates that it contains two strands . The two strands are kept together by the base pairs.
The next drawing illistrates this.
The two strings curve around each other to form a sprial structure or a double helix.
The next drawing gives a schematic view of the structure of the double helix. It illustrates that the back bone of the strings consist of phosphate (P) and sugars (S). The sugar is deoxyribose. ( The ordinary sugar we all know is cane sugar and constist of two glucose molecules)