Giving Tuesday is a global movement which always takes place on the Tuesday following Thanksgiving here in the United States.  This year that means December 3rd.
Giving Tuesday is meant to encourage people to give back either through volunteering, donating to a charity or using their voice in their community. By doing this, we are supporting our communities.

According to nonprofitssource.com...
Giving Tuesday which began in 2012, continues to grow each year and it kicks off the charitable season during a time when many are focusing on their holiday and end-of-year giving. In fact, if you have someone on your holiday shopping list who is impossible or hard to buy for, you can donate to a local charity in their name.  Who doesn't appreciate that?