Welcome to the forum and the USA.
Steph summed it up pretty well, mostly it's about being thankful for what we have and spending time with family and friends.
Hope your first Thanksgiving is one to remember
'I will live in the Past, the Present, and the Future!' Scrooge repeated, as he scrambled out of bed. 'The Spirits of all Three shall strive within me. Oh, Jacob Marley! Heaven, and the Christmas Time be praised for this! I say it on my knees, old Jacob, on my knees!' (Charles Dickens A Christmas Carol)