They simply consist of glass, screen and a frame to protect the glass. This frame is than transfixed to the window space. Casement windows are the most popular as they are designed with a fix part at the top. However, the fixed part can also be designed at the bottom if that is your preference.
The main concerns of fixed windows are usually ventilation versus aesthetics. While picture windows are aesthetically pleasing and energy efficient, they are not designed for ventilation. However, they do provide superior protection from harsh weather conditions.
The primary advantage of fixed windows is that the frame can be designed for tempered or stained glass in order to minimize sun glare. Often places of worship will opt for fixed windows beautifully designed with scenes depicting various religious passages while offices utilize fixed windows to beautify the interior of their building.