Agile is a type of SDLC model, so it's not contrasting to SDLC, but it differs significantly from traditional models like Waterfall. Agile is known for its flexibility. It allows changes to be made in the project requirements even at a later stage of development. Traditional SDLC models like Waterfall are more rigid. Additionally in Agile, working software is delivered frequently (weeks rather than months) in increments, which allows stakeholders to receive tangible progress and provide feedback early and often. Traditional SDLC models typically deliver a complete system at once, near the end of the project lifecycle.