This document discusses wireless communications and ad hoc networks. It begins with an introduction to wireless communications, including the generations of wireless technologies and the electromagnetic spectrum used. It then covers wireless computer networks, focusing on wireless local area networks (WLANs) and describing the IEEE 802.11 standard architecture. This includes components like access points, basic service sets, and extended service sets. It also discusses security issues with wireless networks and ad hoc networks, which are decentralized peer-to-peer networks without a central access point. In the end, it provides some references for further reading on these topics.