OPK vs. basal thermometer

Stacie β€’ Mother to Ben πŸ‘¦πŸ½, Bash πŸ‘¦πŸ½, and Braxton πŸ‘ΆπŸ½, 420 enthusiast πŸ”₯πŸ’¨, lover of life 😍🀘🏾
What's the difference between an OPK and a basal thermometer? Don't they both just tell you when you're going to ovulate?