Over the course of the holiday season, there will be a bunch of free games from the company. If you missed the first free game, you won't be able to claim it.
I wrote about the current free game on Friday, and it's called Horizon ChaseTurbo. It is not known what the next game is until it is available on Saturday. If you want to grab the rest of the free games over the course of the promotion, you might want to set a daily reminder to visit the Store's home page.
The store has an annual holiday sale with free stuff. There are a lot of games on sale, including 25 percent off Spider-Man Remastered and 50 percent off Tiny Tina'sWonderlands. You can get 25 percent off games when you spend more than a certain amount. You can only use coupons with full games, not DLCs, preorders, or in-game currency.
From now until January 5th, there will be free games and a holiday sale. The annual Steam sale will start on December 22nd.