Gift from a foreign persons (parents living abroad)

Hi

I am a green card holder and my parents might give me a gift (less than $50,000). I learned from IRS document that there is a requirement for filling the gift over $100,000. If I receive a gift for less than $100,000, what kind of obligations I have. Does it need to be reported in any other document? As there is no tax on gift amount, I assume that this does not go into my tax return for this year. 

I also have two additional questions.

1) If I and my wife are filing the taxes jointly, will she get the similar amount of exemption

2) Does this $100,000 limit is per year or per lifetime. If it is lifetime limit, I want to be able to carefully document and monitor the limit (though I do not think I will reach this limit ever)

 

I want to make sure that I fully understand my obligations so that I am prepared when I do the taxes. I also want to make sure that I am following all the rules and regulations properly. Your assistance is highly appreciated.