Risk management involves identifying, assessing, and responding to risks throughout a project's lifecycle to meet objectives. It protects the project's scope, time, cost, and quality. Key activities include planning risk management, identifying and analyzing risks qualitatively and quantitatively, planning responses, and monitoring and controlling risks as the project executes. Challenges can include inadequate planning, poor scope definition, inaccurate cost and time estimates, which may require revising plans and estimates and clarifying scope with stakeholders.