Remote sensing (RS), geographic information systems (GIS), and the Global Positioning System (GPS) form the core of geospatial technology, enabling the acquisition and analysis of spatial data. This chapter introduces the fundamental concepts, history, and principles of remote sensing, a vital tool for studying the atmosphere and Earth’s surface without direct contact. The chapter begins by defining remote sensing, its evolution, types, and applications, emphasizing its role in monitoring and analyzing Earth’s processes. Key topics include the electromagnetic spectrum, mechanisms of radiation interaction, and the concept of spectral signatures, unique patterns of reflectance and emission that differentiate materials. Additionally, the chapter discusses components of an ideal remote sensing system, passive and active systems, and data processing stages, providing a comprehensive framework for understanding this technology. By exploring these foundational principles and critical knowledge, the chapter prepares readers to engage with advanced remote sensing applications and technological developments in subsequent sections.