When to use parenthesis and parentheses is a sentence?

International answer Parentheses:

refers to the curved punctuation that we add the to sentence.

Parenthesis:

Refers to the Words that are contained between the two parentheses.

Example: Avoid the use of parentheticals in a sentence (that goes for you too), until you know what they are called. ;)

Here the parenthesis:

-that goes for you too-

...is contained inside the parentheses:

-()