Dual in-line package
Dual in-line package is a term from the computing industry. Integrated circuit chips are small, and have many leads, and it was not generally practical to connect them directly to circuit boards. Instead, after being tested, they were encapsulated into standard sized packages. Circuit boards were designed to have the easier to handle packages connected to them. Alternately, sockets for the packages were designed, and the sockets were connected to the circuit board, allowing the replacement of chips. Memory chips can usefully be replaced with larger memory chips, when prices drop, so they are sometimes socketed.
The dual in-line package is one class of standard packaging form factor, with a row of equally spaced circuit leads down two opposing sides of a plastic or ceramic outer coating for an integrated circuit chip.