In South Korea, the conflict between development and conservation policy still exist among government ministries, and conventional development plan often has priority over conservation policy. Establishment of sustainable development and comprehensive management policy employing the results of ecosystem service studies are highly warranted, but researchers in South Korea are still limited and often misuse the concept of ecosystem services. Thus, we aimed to introduce the concept of Ecosystem Service (ES) and related terminologies such as Social-Ecological Systems (SESs), ecosystem function, trade-off, and human well-being in this paper. Additionally, this article reviewed and arranged key approaches in ES studies as follows: 1) field works, 2) mapping ecosystem services, 3) valuing ES, 4) quantifying trade-offs between ES and 5) understanding SESs. Based on those results, we suggest that field works for basic information have the first priority to be conducted among ES studies. Once basic information is sufficiently accumulated, researchers can perform applied ES research with accuracy. Finally, results of ES studies conducted by five approaches allow decision makers to consider both natural system and society simultaneously, and hence the results can be utilized for sustainable development and conservation policy based on ecosystem-based management.