Sometimes, a noun does not need an article. If we are referring to a general idea, usually a noncount noun, no article is needed.
School is difficult in the summer. (general, all schools)
A school should be clean. (general, yet one example of a general subject)
The school is far from here. (a specific school)
Cats are either hated or loved. (general)
The cats of Africa include lions and cheetahs. (specific)
Do you like chocolate? (general)
Do you have the chocolate I like? (specific)