The most reliable sources consist of .edu and .gov websites and primary sources. These websites are heavily researched and peer-reviewed, and the information is well funded and made by well-educated and trustworthy people. Primary sources are also the best you can choose and derive evidence from, as primary sources are the "original" sources you could say, as they are. Reliable sources such as these .edu and .gov websites, along with primary sources, are important to be used in the research process for many reasons. The main reason is to have accurate data and trusted data that others can peer review and agree that evidence from these sources is reliable and trustworthy.