The Chaine Turn- a series of half turns flapping your body for each turn.
Three Step Turn- you may do it like 'a spiral turn using 3 steps' as demonstrated in the clip of '11 elementary turns and spins in dancing'. However, as you advance, your instructor will tell you to close feet at the turn.
When you are a beginner, your Three Step Turn may look the same as a Chaine Turn, but when later on you close the feet at the turn, you can see the difference.
Good luck with your dancing, maybe you can also check here to see the Dance Glossary.
Part 2- Chain Turn & Three Step Turn
Part 4- Salsa SpinsTricks
Part 5- Tips for beginnersPart 6- The use of Body
........................................................................