Whats The difference?

What is the difference between a High Poly and a Low Poly object?

What are the advantages and disadvantages of each?

I Have an idea of it been about detail? am i right?

poly count refers to the number of polygons that make up the object (triangles usually)

so a simple cube, for example, would have a poly-count (in theory) of 12 tri’s.
(six squares, of two tris each)

The advantage of more poly’s is more detail in your object. More poly’s = more detailed mesh

of course the more geometry on an object, the more memory it takes the computer to calculate, so that would be the disadvantage. If I have a character with 200,000 polys, it may cause much more lag on the game than a character with only 20,000 polys, obviously.

with a character, it is particularly important to keep an eye on poly count and not get carried away…

with static objects (like the environment), depending on your target platform, you can get away with more polys I think, but it really just depends, since performance of a game is cumulative, poly count is just one of many factors which may or may not eat up your RAM

as a rule of thumb when modelling, it’s ALWAYS best to keep the poly count as low as you can manage whilst achieving the desired appearance (beware of Turbosmooth!)