Thanksgiving which falls on the fourth Thursday of November, is one of the biggest American holidays. This holiday started in the early 1600's after settlers arrived in America. These people who came from Europe didn't know how to survive in the wild new country. Luckily, they met some friendly American Indians, who showed them how to hunt turkeys and grow corn. In the fall, after the harvest, the settlers had a great feast. They invited the Indians to thank them for their help.
Today the tradition continues. On Thanksgiving Day, Americans invite their friends over for a turkey dinner and give thanks for what they have.

"falls" in the text means "comes"
on holiday(美)   on vacation(英)
settle down  v.定居, 平静下来, 专心于    还有：He hasn't settle down. 指单身
ancestor 祖先       tell me about sth about anestry 祖籍
jerk = turkey  怪才，怪人    a slang word  不说：a slang   slang是不可数
Quit smoking cool turkey.     cool turkey = once and for all 一劳永逸
feast 盛宴 -- a great meal for special occasion
treat sb to sth 请sb做sth   on Teacher Day  on Labour Day
This food(dish) looks inviting/attractive.
corny 陈腐的,土的
He is raising chickens.  growing corn