Usage of 'either' without 'or'
I am aware of the usual 'either....or' way of constructing a sentence.. for eg: Either you have the cake or i will.

But how to use only 'either' and is it correct?
For eg: It is not difficult either.
1) How to interpret the above sentence exactly?
2) I am particularly looking for the meaning of the construction ' not (negation).... either'

Question

Usage of 'either' without 'or'
I am aware of the usual 'either....or' way of constructing a sentence.. for eg: Either you have the cake or i will.

But how to use only 'either' and is it correct?
For eg: It is not difficult either. 
1) How to interpret the above sentence exactly?
2) I am particularly looking for the meaning of the construction ' not (negation).... either'

Answer

I would make a sentence like this:

"Learning to speak English is not boring, and it's not difficult either."

"Isn't pretty, and it's not smart either."

"Sally didn't give you the money, and I didn't give it to you either."

In these sentences, "either" is like the opposite of "too".

Jane *is* a teacher, and I am *too*.
Jane *is not* a teacher, and I'm *not* either.

--or--

Jane:  I like apples!
Bob:  Me too!

Jane: I don't like apples!
Bob:  Me neither!

Hope that helps!

Answer

This sentence completes a previous statement:  e.g., "Cooking oatmeal doesn't take very long."  The listener then adds information:  "It's not difficult, either."  (I.e., "Cooking oatmeal is neither time-consuming nor difficult.")

re. "not either":  "The soup is not hot, but it's not cold, either."  This could be two sentences in a dialog:  
A.:  "This soup is not hot!"
B.:  "But it's not cold, either.  It's just lukewarm."