Cooperative learning is an instructional strategy where small groups of 2-6 students work together to maximize individual and collective learning. There are five key elements: positive interdependence through shared goals and materials; individual and group accountability; interpersonal skills like communication; face-to-face interaction to help each other learn; and group processing through self-assessment. The phases of cooperative learning include preparation, instruction, assigning roles, monitoring, assessment, and challenging group dynamics. Common techniques include STAD, Jigsaw, Think-Pair-Share, Numbered Heads, and Team-Pair-Solo.