Open Science is basically all about free access to research publications and research data. The advantage of Open Science is that researchers increase the impact of their research. Your research reaches a broader audience and the possibilities for more citations increase. Many licencees demand that funded publications and research data are made publicly available - Open Access (OA). Read more about Open Access to research publications and research data at the website of the Ministry of Higher Education and Science.
The advantages of Open Science briefly:
Learn more about Open Science at the EU project homepage "Fostering the practical implementation of Open Science in Horizon 2020 and beyond" (FOSTER Plus).