John Bardeen, Walter Brattain, and William Shockley invent the point-contact transistor (when they first observed the effects) and pretty much paved the way for the modern electronics revolution as the transistor is the fundamental building block of modern electronics technology.
As defined by Wikipedia, a transistor is a semiconductor device (with at least three terminals) used to amplify or switch electronic signals and electrical power. A voltage or current applied to one pair of terminals controls the current through another pair of terminals. When they are combined in integrated circuits, as they normally are today, they can create logic gates, and that’s the fundamental building block of modern computers. (The other primary components of an integrated circuit are diodes, resistors, and capacitors.)
Without transistors, we’d still be computing using vacuum tubes using machines that take up entire rooms and only using computers for mathematical calculations. The inventors were truly deserving of their nobel prize.