Most of the approved COVID-19 vaccines are currently mRNA vaccines https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/mrna.html, which are a new (but not unknown) type of vaccine. mRNA vaccines do not use live virus so it cannot give you COVID-19 and messenger RNA (orMRNA) is genetic material that tells your body how to make protein that will trigger an immune response. When you are vaccinated with COVID-19 mRNA it teaches your immune system how to make copies of the spike protein, so that if your body is exposed to the actual virus it will recognise it and know how to fight it off.
