I think your question also refers to right side (RS) or wrong side (WS).
If you are working stockinette the RS or front would be the knit side. If you're working reverse stockinette the purl side would be the right side. Garter stitch is the same on both sides. Usually a pattern will specify which is the RS and which is the WS and you can mark it with a safety pin or piece of yarn so you know which side is which..