Over the past two decades, Wi-Fi technology has demonstrated its highly viable nature through rapid iteration. Approximately every 5 years, a new generation of Wi-Fi specification is ratified and quickly becomes dominant in the market. Such evolution is primarily driven by the growing bandwidth capabilities of the broadband access technologies, the widespread adoption of Wi-Fi based smart devices, and the emergence of various new services in the wireless network environment. Wi-Fi has already become an indispensable part of our daily life. This chapter serves as an introduction to the evolution of Wi-Fi standards and the overall landscape of Wi-Fi technology. It aims to provide fundamental knowledge to readers who may not be familiar with Wi-Fi technology, ensuring they gain a basic understanding of its principles and development, including both Physical Layer (PHY) and Medium Access Control (MAC) specifications. With this foundation, readers will be better prepared to comprehend and grasp the advancements and potential of Wi-Fi 6 and Wi-Fi 7, which are discussed in the following chapters.