Atmospheric pressure plasmas have been investigated intensively to evaluate the potential utilization of the plasmas in processing gas, liquid, organic, and inorganic surfaces due to their unique characteristics and advantages. In particular, nonthermal and spatially uniform glow discharge plasmas have been actively studied and adopted in diverse application fields. By considering the new technology trend and unique application areas of atmospheric pressure plasmas, the main target of research topics and plasma source development may include the following keywords: large area, discharge in open air, low gas temperature, arc or filament free, and optimization for specific applications. In this entry, we follow this line of inquiry by focusing on an understanding of basic physics, source development, and characterization methods of atmospheric pressure uniform glow discharges (APUGDs). For fundamental study, the effects of various external parameters such as input power, discharge gap distance, gas type, dielectric, and driving frequency in a typical radio frequency (RF) capacitively coupled plasma source are discussed. A concept for large-area RF APUGD source is discussed with a few examples. Some spectroscopic diagnostics that are more favored in high pressure plasmas to measure plasma parameters are briefly introduced. In addition, due to their unique plasma characteristics, emerging application fields of APUGD such as biomedicines, agriculture, and food sciences are described.