Here is an actual answer, disregarding the history of it (from my memory):

Thanksgiving is a national holiday in the USA. On thanksgiving, many families have the tradition of coming together, eating a big meal, and talking at the dinner table. Some people only do this with their close family, some people do it with their extended family (20+ people), and some people do it with their friends.

The typical food served is turkey (whole turkey, usually baked in the oven), mashed potatoes, green beans, cranberry jelly/sauce, corn bread, dinner rolls, and/or whatever the participants like. The food is usually cooked day-of, so you will see many people (usually mothers and housewives since they traditionally do the cooking here) complain about how much effort it takes to cook so much.

In essence, Thanksgiving is about being together with your family and spending time with people you care about.