High poly versus low poly
The poly count is the number of polygons (or faces) in a mesh. This number is important because it gives a very good idea of the complexity of a mesh. A mesh with eight million polygons is going to be a lot heavier computationally than a mesh with eight hundred polygons.
High poly
A high poly count is generally anything in the millions. Meanwhile, a low poly count would be anything up to a few hundred. Everything in between is medium.
Meshes with high poly counts are referred to as high poly. These meshes are generally more difficult to work with because they can slow down Blender a bit (it’s hard for Blender to manage 20 million vertices at once!). However, they are still used for some things because of the immense detail they offer. For example, high poly meshes are often used for sculpting, when extreme details are needed, or for professional visual effects projects. More, tinier polygons make for a more detailed model than fewer, bigger...
