Quotient stacks

A quotient stack is a mathematical concept used to study how a group acts on a space, capturing not just the shape of the space but also the symmetries involved. Think of it as a refined way to "divide" a space by a group, accounting for points and the symmetries that relate them. Unlike a simple quotient (which might overlook some symmetry nuances), a quotient stack records the full group action structure, making it a powerful tool in areas like algebraic geometry for understanding shapes with symmetries at a very detailed level.