What is an explanation of the file modes briefly?

Two file modes are "text" and "binary". Text is used for human readable data, such as a C source file, or a notepad text file. Binary is used for computer readable data, such as an executable object file.

Two other file modes are "sequential" and "random". Sequential is used when the file is accessed serially, from the beginning to the end, and can be used for both text and binary files. Random is used when the file is accessed non-serially, often jumping around from place to place. An example of random is a database file.