What is a caucus, and what events led to its demise as a method for nominating candidates?

People who are generally like-minded who normally meet up to decide to whom they would cast their vote are called Caucus.

Explanation

In earlier times, it used to be a private gathering or meeting, but it eventually faded away as political parties came into existence with more prominence, led to its membership getting broadened. As increased Democratic spread led to oppositions to Caucasus, more people criticized it due to closed dynamics. Leaders such as Jackson, Quincy and Clay boycotted it due to its closed process.