Traditional lectures often involve students passively listening to an instructor read slides or share information. In contrast, active learning is an umbrella term that refers to any activity that invites students to be engaged participants in their own learning process. When students are actively engaged in their learning they are more motivated, able to learn the material better, and retain it longer.
Activities that leverage active learning can be either individual or group-based and often include elements of reflection, sharing thoughts and perspectives, synthesizing information, and making real-world connections. Active learning can easily be incorporated into a variety of instructional strategies including lecture-based instruction and it is central to many of the contemporary methods such as flipped classrooms, case-based learning, and problem-based learning. Whichever active learning techniques you choose to use, think about how you will create an inclusive environment where all students are comfortable sharing their voice and have access to the materials and discussion.
These activities may be new to students and they might experience some apprehension around it. Be sure to explain to students why you are asking them to do this, and what your expectations are.
Image modified from: https://cei.umn.edu/teaching-resources/active-learning
These activities and many, many more can be found on this great list of active learning techniques.