What is mean by single stranded flagella in prokaryotes???

Prokaryotes are microscopic organisms belonging to the domains Bacteria and Archaea, which are two out of the three major domains of life. (Eukarya, the the third, contains all eukaryotes, including animals, plants, and fungi.) Bacteria and archaea are single-celled, while most eukaryotes are multicellular.Fossils show that prokaryotes were already here on Earth 3.53.53, point, 5 billion years ago, and scientists think that prokaryotic ancestors gave rise to all of the life forms present on Earth today^{2,3}