This document discusses brain-computer interfaces (BCI). It begins with an introduction and overview of BCI technology and how it aims to create a direct channel between the human brain and computers. It then covers the basic principles and components of BCI systems, including electroencephalography (EEG) and different types of invasive and non-invasive interfaces. Applications are discussed such as communication devices for paralyzed patients and control of prosthetics. Advantages include improved quality of life and new areas of research, while disadvantages include health risks, required training, and costs. The document concludes that BCI is an advancing technology with promising applications in rehabilitation and human enhancement.