What is the difference between So and Too?

So: 

1- It describes something either positive or negative. 

2- To emphasize and make the statement stronger. 

3- It is an informal meaning of very.

Example:

He studied so much and got a full mark.

Too:

1- It has an excessive meaning (more than enough).

2- It describes a negative situation. 

Example:

He studied too much, yet he didn't get a good mark.