Bejeweled is the game that invented the modern match-three. PopCap released it in 2001 as a browser game called Diamond Mine, and every match-3 since — Candy Crush included — is a descendant. Swap two adjacent gems to make a line of three or more, they vanish, the gems above fall, and if that fall makes another match you get it for free.
The original is a pure endless mode: no lives, no move limit, no energy timer. It gets faster and denser as your level rises, and it ends when there are no valid swaps left on the board.
It's the one that defined and popularised the genre. PopCap released it in 2001 as Diamond Mine in the browser, and it became the template that Candy Crush and hundreds of others followed.
Cause cascades. Making matches near the bottom of the board sets off chains of free matches above, and those chains are worth far more than the individual match that started them.
Yes — a light browser game with mouse or touch controls and nothing to install.