What is the Function of Gelatine
It really depends on how much of it you're using.

If it's only a small amount, it might be for mouthfeel -- it'll make the liquid more viscous and less 'watery'.  Consider a good chicken soup, where the broth has a bit of body to it.

If it's a large amount, it's to get the liquid to set up.  In something like a panna cotta, aspics, mousse, or a no-bake pie, it's to get the liquid to firm up and become either solid or at least scoopable.

And gelatin doesn't need to be used in solely liquid dishes -- America's Test Kitchen used in a meatloaf recipe for what was most likely mouthfeel.

... but it's possible that there are other uses.  I seem to recall hearing that it can be used to clarify broths as well.