Community colleges are two-year colleges. They are typically open to everyone who wants to enroll. They can be a very important tool for developing human capital in a given area.
One of the most important reasons to have a community college is to teach skills that students can use in the workforce. Community colleges typically have some programs that are not academic but are, instead, more vocational. Because they offer such courses, community colleges can develop human capital. They can create a more skilled workforce in an area, thus allowing it to have more economic potential.
A related reason why community colleges are important is because they can help people who would otherwise not be able to get any higher education at all. Many community college students are non-traditional students (often, they are older adults coming back to try to get more education). For such students, the cost of attending a four-year college would be prohibitive. Community colleges allow such students to improve themselves in ways that they otherwise might not be able to achieve.
Finally, community colleges can be beneficial to people who intend to complete four-year degrees. They are typically very low-cost (in my state, they are free to qualifying high school students). This allows people to take two years of college classes at a much lower price than they would incur if they went to a four-year college right away.