{math-operators} is about operators in math mode. These include sums, integrals and similar, text operators like sin, cos, etc.

Operators in mathematics, typically sums, integrals and similar symbols, as well as ones defined using \operatorname or \DeclareMathOperator.

Here belongs questions concerning creation of new operators (both symbol and text ones), limits placement, spacing around operators etc.

The two most used packages for operator manipulation are amsmath and mathtools.