Every TWO DAYS là gì

I'm preparing IELTS which is an English test, and there was this question

Audio script : "... every second day we went to one of the big hospitals and worked there."

Question: How often did they work in a hospital?
Answer: Every 2 days

I wonder this is a typo or every second day means exactly same as every 2 days.

and is that like say they worked on 1nd of July, and then on 2nd of July they take a rest, and work again on 3rd of July, and so on.

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