A filesystem is a method used by operating systems to organize and manage data stored on storage devices like hard drives and SSDs. It defines how files are named, stored, and retrieved, allowing users and applications to access data efficiently. Common types of filesystems include NTFS, FAT32, and ext4. Filesystems also manage metadata, which includes information about files such as their size, creation date, and permissions. This organization helps ensure data integrity and security, making it easier for users to navigate their data and for systems to perform tasks like backups and file sharing.