What is a DB25 connection?

A type of D-Sub connector. DB-25's are commonly found on computing equipment where they are employed to connect peripherals. They are common to parallel ports or RS-232 ports on PC computers, but also often used in a variety of ways in the audio community. For example, TASCAM commonly uses the DB-25 connector for analog and/or digital I/O on their products, as do some other brands.