The file system provides the mechanism for online storage and access to file contents, including data and programs. This paper covers the high-level details of file systems, as well as related topics such as the disk cache, the file system interface to the kernel, and the user-level APIs that use the features of the file system. It will give you a thorough understanding of how a file system works in general. The main component of the operating system is the file system. It is used to create, manipulate, store, and retrieve data. At the highest level, a file system is a way to manage information on a secondary storage medium. There are so many layers under and above the file system. All the layers are to be fully described here. This paper will give the explanatory knowledge of the file system designers and the researchers in the area. The complete path from the user process to secondary storage device is to be mentioned. File system is the area where the researchers are doing lot of job and there is always a need to do more work. The work is going on for the efficient, secure, energy saving techniques for the file systems. As we know that the hardware is going to be fast in performance and low-priced day by day. The software is not built to comeback with the hardware technology. So there is a need to do research in this area to bridge the technology gap.