The need to understand insect ecology, biology, and behavior is critical to combat the rapid loss of biodiversity from direct anthropogenic activities and climate change. This chapter provides an overview of factors shaping species distributions, populations, species interactions, communities, ecosystems, and sampling methods to collect data on insects. Through knowledge of insects, we can better understand ecosystems, habitat restoration practices, natural resource management, and biodiversity conservation. Also, case studies are provided to illustrate the theoretical part of the chapter. The information is useful for biodiversity managers and policymakers.