Tokui vs Jyozu

What is the difference between Tokui (good) and Jyozu (skillful) ?

It seems when trying to say "I'm/You're  'good' at something, sometimes the Rocket Japanese lesson uses Tokui and sometimes it uses Jyozu.  What  is the criteria for using these two words?  

Jouzu is something you are good at or have clever skills at. Tokui is a strong point of ability. 

こんにちはSheryl21さん and Tony-S10さん！

In addition to what Tony-S10さん said, you would generally not use「じょうず」for yourself, as it might come off as a bit prideful. This also applies to its counterpart,「へた」.

Because of this, you would usually use「とくい」and「にがて」when you are speaking about yourself.

I hope this helps, and please do not hesitate to ask if you have any other questions.
がんばってくださいね！

Crystal

Thank you!  This explanation is great!  
 

This explanation is very helpful. I would also appreciate if someone could shed some light on how to determine when it's 「じょうず」vs 「おじょうず」。

That is easy, you put "お" before words when you are trying to be more polite. As you may know there are varying levels of politeness in Japanese depending on whom you are addressing. In this case if you were talking to someone you know well じょうず would be used. If you were talking to a stranger or your fiancee's boss おじょうず would be used.

Thank you. It often trips me up when I do the "Know It" and Flashcard sections.