True meaning of thanksgiving religious

Merriam-Webster defines thanksgiving as "the act of giving thanks; or a prayer expressing gratitude." Is this also the Christian meaning of "thanksgiving"?

What exactly should Christians give thanks for and why? 

"Giving thanks always and for everything to God the Father in the name of our Lord Jesus Christ" ~ Ephesians

Discover the true meaning and significance of thanksgiving in the Christian faith and the biblical definition of this virtue.

Christian Meaning of Thanksgiving

The spiritual person is the one who is thankful for everything.

He is the one who receives everything with thanksgiving and who knows that he has nothing except what he has received from God. 

"A person cannot receive even one thing unless it is given him from heaven." (John )

"Every good gift and every perfect gift is from above, coming down from the Father of lights with whom there is no variation or shadow due to change." (Jame