Alabama, Land of the Absurd. | You asked for simple explanations, but your questions can raise some rather complex issues.
Here is a fairly "simple" explanation of the federal estate tax (this is for the FEDERAL tax only), some states may have their own estate or inheritance taxes (google, "your state" and inheritance tax or estate tax).
As you will note, the rules just changed January 1, 2013.
https://www.fidelity.com/viewpoints/new-estate-tax-laws
Here is an explanation of the FEDERAL gift tax. This should answer your last question. As always, seek competent legal advice to see how these rules apply in your circumstance and YOUR STATE.
http://fairmark.com/general-taxation/tax-rules-for-gifts/ |