Memory pages are fixed-size blocks of memory used by an operating system to manage and allocate memory efficiently. Each page typically contains a set amount of data, allowing the system to organize and access memory in a structured way. This helps in optimizing the use of physical memory and reduces fragmentation. When a program runs, its data is divided into these memory pages, which can be loaded into and out of the RAM as needed. This process, known as paging, allows the system to use virtual memory, enabling larger applications to run even if the physical memory is limited.