A JRPG, or Japanese role playing game, is a role playing game in the tradition established by Dragon Quest in 1986 and Final Fantasy in 1987, typically featuring a predefined party, a strongly authored story, and character progression through levels and equipment.
Western computer RPGs of the 1980s leaned toward open ended character creation and player directed exploration. The Japanese console tradition took the same tabletop roots and shaped them for a controller and a television: a fixed cast with written personalities, a linear to semi open journey, frequent turn based or menu driven combat, and long story sequences between towns, dungeons, and boss fights. Dragon Quest made that form a mass audience phenomenon in Japan, and Final Fantasy added more elaborate stories and presentation.
The label today describes a style more than a passport. Games made outside Japan that use a predefined party, authored story, and turn based systems are routinely called JRPGs, while Japanese made RPGs with real time action and created characters, such as Dark Souls, are routinely not. Debates about the border are constant because the category is historical, not technical.
Modern entries vary the formula freely, with action combat in recent Final Fantasy games, social simulation in Persona, and vast open areas in Xenoblade Chronicles. What survives across all of them is the emphasis on a specific group of characters whose relationships carry the story from the first town to the final boss.
In play"If you want a long authored story with a fixed party, pick a JRPG over a create your own hero RPG."