I don't get it.
Here are some examples of the sentences without article.
I go to school.(the school I usually go to/Maybe I am a teacher or a student or a staff of the school.)
I go to a school.( a school in general, not the school I usually go to)
I go to the school.( a school I visit)
I go to hospital.(Maybe I am a doctor or a patient. )
I go to the hospital. ( I visit the hospital to see a patient.)
I hope someone can explain it to you more.
Have a good time.