I am not seeing the difference in a sea /es decir

Question

I have read through the explanations and have tested, but I really can't not differentiate the type of sentence between the two uses or concepts. Is there any other way to explain this, or some cue that might help me?

Thanks!

Accepted Answer

Hola Papi
As it says in the lesson, there is no difference, they both mean the same thing. 
The only difference is in register, in this case the level of formality:

"o sea" is more colloquial (less formal)
"es decir" is more formal

This is why when you test you will see the hints guide you as to whether the speaker is being more or less formal.
I hope this clarifies things for you.
Saludos 
Shui

Answer

Thank you!   Yes, that did help.  The key is in the hint (colloquial/formal)!