Agile project management grew out of software teams’ frustration with plan-driven development, where requirements were fixed early and problems surfaced late. This paper traces its history from Royce’s 1970 waterfall model to the 2001 Agile Manifesto, then compares three frameworks: Scrum, Kanban, and Extreme Programming. It reviews the empirical research, including Dybå and Dingsøyr’s 2008 systematic review and Serrador and Pinto’s 2015 study of about 1,000 projects. Both link agile to better outcomes, though the evidence is uneven. The paper also covers common adoption problems: resistance from management, difficulty scaling across many teams, and agile practiced in name only. Results depend less on which framework a team picks than on organizational culture and how well the method fits the project.