COM(2020) 301 final - A hydrogen strategy for a climate-neutral Europe
https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX:52020DC0301&from=EN

‘Low-carbon hydrogen’ encompasses fossil-based hydrogen with carbon capture and electricity-based hydrogen, with significantly reduced full life-cycle greenhouse gas emissions compared to existing hydrogen production. 

The distinction between low-carbon hydrogen and renewable hydrogen is that the latter is defined by the energy sources it uses, such as wind, hydro and solar power, while the former is defined by the amount of GHG emissions it produces and is neutral to the method used. As a result, low-carbon hydrogen can come from a variety of energy sources such as natural gas with CCS or electrolysers running on nuclear electricity.