It is possible to cram dozens to millions of transistors and passive elements onto a single slab of silicon. This is known as an integrated circuit, or IC.
Integrated circuits come in different packages. The package refers to the type of exterior casing that the connects the actual integrated circuit chip to its input and output pins. A common type of package is the Dual-In-Line Package, or DIP. This package contains a rectangular box with two rows of pins coming out of the long edge. The number that succeeds "DIP" denotes the number of pins in package. The package often has an indentation or dot at one end to help identify the pins.
Since integrated circuits are sensitive to heat, a socket is often first soldered to the board, and the IC package then plugged into the sockets. Sockets are also useful if the chip might need to be swapped.