The term "df" commonly refers to a command used in computer systems, particularly in Unix and Linux environments. It stands for "disk free" and is used to display the amount of disk space available on file systems. The command provides information about total space, used space, and available space, helping users manage their storage effectively. In programming, "df" can also refer to a data frame, a data structure used in languages like Python and R. A data frame organizes data into rows and columns, making it easier to manipulate and analyze datasets in data science and statistical applications.