Ballpoint pens were invented in the 1940s, although earlier efforts to design them dated back to the 1800s. By the 1950s they'd become standard technology, displacing the traditional fountain pen. Ballpoint pens dispense their ink via the rolling action of a small metal sphere or ball at the tip, rather than a nib.
At the end of World War Two, Eversharp produced one of the first commercial ballpoint pens, called the Eversharp CA for capillary action. Reynolds followed suit with a ballpoint pen called the Reynolds Rocket. These two pens were sold for the same price as high-end fountain pens, and both failed because they had problems with leaking.
Just when it seemed the prospects for ballpoint pens were dim, around 1950, Marcel Bich pioneered a very inexpensive ballpoint, the Bic Crystal. It was a self-contained disposable ballpoint pen that became the genesis of the Bic pen company.
Suddenly, every major pen company (Sheaffer, Parker, etc.) that wanted to survive had to come out with a ballpoint pen. Thereafter, ballpoints came in two varieties: inexpensive writing instruments and higher-end fashion statements and gift items (e.g. Cross and Parker ballpoints).