What is an example network mask?

Could you elaborate on what constitutes an example network mask? In the realm of networking and IP addressing, a network mask is crucial for determining which parts of an IP address represent the network portion and which represent the host portion. An example would greatly assist in visualizing this concept. Say, for instance, if we're dealing with IPv4 addresses, could you provide a specific IP address along with its corresponding network mask to demonstrate how it functions? This would help me understand the application of network masks in practical scenarios.