Hacktoberfest is an annual, month-long event designed to motivate people to contribute to open-source projects on platforms like GitHub. Usually, it happens around October. A certain number of pull requests (contributions) to open-source repositories must be made by participants during the month. Hacktoberfest seeks to assist in the expansion of the open-source community, foster developer experience, and encourage open-source cooperation. It's a fantastic way for both novice and seasoned developers to get involved in the creation of open-source software.