In the broadest terms, virtual labs are on-screen or online simulators that help test ideas and observe results. Researchers and students alike use them to perform experiments to either study a variety of outcomes, or to obtain a desired result.
There are many kinds of virtual labs, which range from simple video animations with limited interaction and variables, to 3D experiences that recreate as much of a physical experience as possible on screen.
Results of experiments done through virtual labs can be saved, compiled, and studied to see how and why the results came out as they did.
In education, virtual labs present a viable alternative to physical labs—they require no dedicated space or expensive (or dangerous) chemicals and equipment. Experiments can be run as many times as necessary for students to develop conceptual understanding of the topic, and to answer the questions posed by the instructor. These simulations can be teacher-led, used completely independently, or implemented in a hybrid model. And most only require internet access and a subscription to the product to use.