This paper provides a comprehensive survey of variants and extensions of the Resource-Constrained Project Scheduling Problem (RCPSP). The RCPSP involves scheduling activities subject to precedence and resource constraints to minimize the makespan. While the basic RCPSP is well-studied, it often lacks the flexibility to model real-world scenarios. Consequently, various extensions have been developed to address these limitations. The paper classifies these extensions according to the structure of the RCPSP, covering generalizations of the activity concept, precedence relations, and resource constraints. It also discusses alternative objectives and approaches for scheduling multiple projects. The survey includes popular variants such as multiple modes, minimal and maximal time lags, and net present value-based objectives, as well as less-known concepts. The paper aims to provide a broad overview of the diversity of problem settings in project scheduling, focusing on deterministic approaches and recent developments.This paper provides a comprehensive survey of variants and extensions of the Resource-Constrained Project Scheduling Problem (RCPSP). The RCPSP involves scheduling activities subject to precedence and resource constraints to minimize the makespan. While the basic RCPSP is well-studied, it often lacks the flexibility to model real-world scenarios. Consequently, various extensions have been developed to address these limitations. The paper classifies these extensions according to the structure of the RCPSP, covering generalizations of the activity concept, precedence relations, and resource constraints. It also discusses alternative objectives and approaches for scheduling multiple projects. The survey includes popular variants such as multiple modes, minimal and maximal time lags, and net present value-based objectives, as well as less-known concepts. The paper aims to provide a broad overview of the diversity of problem settings in project scheduling, focusing on deterministic approaches and recent developments.