When to use: "Thank you" vs "Congratulations"

The first is about trying to return a favor. You did something for me, so I thank you in return. It also implies you only did that thing because I asked you to.

The later is about rewarding someone for a job well done. It's about recognition and it's about building trust. It is the best way of saying "I'd like you to do more of that in the future", without actually saying it.

If you're a leader and you're trying to build a strong and independent team, remember this.