The massive use of decarbonized and distributed energy resources creates important challenges to guarantee the reliable, safe, and efficient operation of power systems. Power systems are required to use technologies that provide flexibility to the grid to maximize the use of different system resources. In this article, an international review was carried out to identify the different types of grid operation models, the types of flexibility services, and case studies in the implementation of flexibility services. Based on international experiences, the current regulatory framework was analyzed, and gaps were identified at the technological, regulatory, and business levels. A referential model and 5 flexibility services are proposed (voltage control, security, sufficiency, maintenance, and frequency management). Several actions are recommended to enable and facilitate the implementation of flexibility services in Colombia.