Definition:
Inquiry-based learning is a form of active learning. This starts by posing questions, making observations, problems or scenarios- rather than simply presenting facts. This process is mostly assisted by a facilitator. This can be done in multiple formats like field-work, case studies, investigations, individual and group projects, research projects, requirement gathering.
To develop knowledge or solutions, inquirers are done to identify and research issues. Questions are developed which includes problem-based learning which is generally used in projects as well as research. Inquiry-based learning is principally very closely related to the development and practice of thinking skills. Specific learning processes that people engage during inquiry-learning is by creating questions of their own, obtaining supporting evidence to answer the questions, explaining the evidence collected, connecting the explanation to the knowledge obtained from the investigative process, creating an argument and justification for the explanation. There are four different levels of Inquiry based learning i.e. Confirmation Inquiry, Structured Inquiry, Guided Inquiry and Open/True Inquiry. Inquiry requires multiple cognitive processes and variables, such as causality and co-occurrence that enrich with age and experience.
Further Reading:
https://en.wikipedia.org/wiki/Inquiry-based_learning