Gates are constructed of electronic components (transistors, resistors, and capacitors). Initially these components were made from separate pieces of silicon and then they were wired together on a circuit board. The integrated circuit (IC) was invented in 1958. An IC contains these electronic components fabricated together on one piece of silicon. Etching the components on the chip means they can be smaller and use less power than individual components attached to a circuit board. Each IC, also called a chip, contains many gates. The first ICs contained up to 100 electronic components. They were called SSI chips (small scale integration). Current chips contain more than 1 million electronic components. They are called ULSI chips (ultra large-scale integration).
We think of a chip as a little black plastic rectangle with metal legs. This is not the chip, this is the housing. The actual chip is mounted in this housing. The inputs and outputs of the circuit are attached to the pins that protrude from the housing, and those pins are welded to a circuit board so the chip can communicate with other components.
Here is a drawing of a simple SSI IC.
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