Steam Community Items are used to personalize Steam profiles or used in its chat. They can be crafted, bought through Steam Market or bought through the Point Shop. Items from the Points Shop are not marketable or tradeable.
Trading Cards
Foil Trading Cards
Booster Pack
Boosters Packs contain 3 random cards from the set. Booster packs can be purchased in the Steam Market or crafted using 750 Gems.
Steam Badges
Once a set of cards has been collected it can be crafted into a game badge. Badges are tied to user accounts and are shown on users' profiles. Crafting game badges earns the user marketable items like emoticons, profile backgrounds, and coupons. Badges can be leveled up by collecting the set again and re-crafting the badge thus earning more items.
Profile Backgrounds
When you craft a Badge, one of the things you'll receive is a profile background. You can use one of these as a background on your Steam profile page. They can also be bought through the Point Shop.
Animated Avatars
Animated Stickers can be used in Steam Chat or display in Profile Item Showcase. They can also be bought through the Point Shop.
Chat Emoticons
Chat Emoticons can be used in Steam Chat. They can also be received when crafting Steam Badges or bought through the Point Shop.