A project manager is your principal point of contact who is responsible for managing your task from start to finish. In a nutshell, a PM breaks a project into tasks, assigns them to developers, and makes sure that they meet all your requirements in full and on time.
A PM is present at every meeting between you and the team. You can contact your PM at any time during the business day to get updates on the task status or make any requests.
A QA makes sure that the developers have implemented all your technical specifications precisely to guarantee the best quality.