The von Neumann architecture is a model of how computers work. It was developed by John von Neumann, and others in the 1940s. According to this model, a computer consists of two fundamental parts: There is a processor, which loads and executes program instructions, and there is computer memory which holds both the instructions and the data. The von Neumann architecture is probably the most common model that describes how most computers work today. As it was developed at Princeton University, it is also known as Princeton architecture, but that term is less common.
Another very similar architecture is the Harvard architecture, which separates the place where data is held from that where program instructions are held.