e.g. I'm here on the ORBIS plane,"the flying eye hospital."

(In this sentence, why is quotation marks used? What is the difference between with quotation marks and without quotation marks?)

Unless it's a quotation from something, I don't know why that phrase is in quotation marks.

Could it be a phrase used in a brochure or advertisement?

The quotation marks used around "the flying eye hospital" indicate that this is a phrase that is being used exactly as it was spoken, written, or titled. Quotation marks are used to show that the words inside them are a direct quote, a specific term, or a title of something.

In this case, "the flying eye hospital" refers to the specific name or title of the ORBIS plane. By using quotation marks, it distinguishes this phrase from the rest of the sentence, highlighting it as a unique concept or entity.

When quotation marks are not used, it usually means that the words are not being treated as a specific title or exact quote. For example, without quotation marks, the sentence would read: "I'm here on the ORBIS plane, the flying eye hospital." In this case, "the flying eye hospital" is still referring to the unique concept, but it's not being presented as a precise term or title.

So, the use of quotation marks helps to draw attention to specific words or phrases and indicates that they should be understood in a particular way.