Running from 2014-2020, Horizon 2020 is the biggest EU Research and Innovation programme with nearly €80 billion of funding available over 7 years.
On the Participant Portal, the European Commission publishes all the calls of its research and innovation programmes H2020 (link), including additional calls in the Other Funding Opportunities section. You can search according to your research topic with key words and set filters in the H2020 calls list. The H2020 Online Manuel of the EU is available here.
The current main Horizon 2020 work programme comprises an introduction, 18 thematic sections and the general annexes describing general rules such as standard admissibility conditions and eligibility criteria, types of action, selection and award criteria, etc. Each thematic section is self-contained, and describes the overall objectives, the respective calls for proposals, and the topics within each call.
This Horizon 2020 work programme is complemented by the separate work programmes for the European Research Council, Euratom, the Joint Research Centre and the Strategic Innovation Agenda for the European Institute of Innovation and technology (EIT).