Project-based learning (PBL) is a teaching approach where students learn by being actively involved in a real-world and meaningful project. They may create a product or a presentation for a real audience.
When kids engage in this type of learning they can gain essential knowledge and skills like critical thinking, collaboration, creativity and communication. The students work on a project for an extended period of time. For example, over a week or even a semester.
The TeachThought Staff have put together 20 Examples of Project-Based Learning. You might want to also check out some identified Outcomes of Project-Based Learning as it is important to have an objective or outcome for why you are planning and implementing a PBL approach.
If you want to be more specific when it comes to subject areas and year levels, then the Buck Institute for Educators has a library of projects for you to explore.