The term hybrid open access refers to the possibility that (especially large) publishers offers authors to make the individual article open access in an otherwise subscription-based journal.
The publishers are usually charging author fees (APC - Article Processing Charges) that are very high. Here are some examples:
If you have received money from a research funder which has an open access policy the fee is covered by that.
2017). Growth of hybrid open access, 2009–2016. PeerJ 5:e3878 https://doi.org/10.7717/peerj.3878(
Boyes, P. & Kingsley, D. (2016). Hybrid open access – an analysis. Retrieved October 12, 2017, from https://unlockingresearch.blog.lib.cam.ac.uk/?p=969