Chapter I provides an introduction to the fundamentals of mapping and geospatial concepts for high school teachers. It starts with an overview of why mapping and geospatial concepts are important, followed by a discussion of the fundamentals of data processing, including data collection, organization, analysis, and visualization. Next, the chapter explains geospatial data, including an understanding of geodata and geographic information systems (GIS) together with examples of its usage. Finally, the chapter delves into the open source philosophy and its applications in mapping, including the use of open source software, open data, and open mapping initiatives. It also describes the most popular open source geotools that can be useful in the high school educational process. This chapter is designed to equip educators with the knowledge and tools necessary to incorporate mapping and geospatial concepts into their curriculum, ultimately helping students to better understand and analyze the world around them.