Foreigners can live in South Korea on various types of visas, depending on their circumstances. Tourist visas are valid for up to 90 days, while work visas are usually valid for one year and student visas for the duration of the studies. Marriage visas are available for those married to a South Korean citizen or permanent resident, while the F-4 visa is available to those with Korean ancestry or who have previously held Korean citizenship. Long-term residency and permanent residency are also options after living in South Korea for a certain period of time. It is important to understand the requirements and limitations of each type of visa and apply for extensions or renewals as needed to avoid penalties.