The app is available for many common mobile devices, including iOS and Android devices. Its primary use is for chat, and it is less suited for other tasks such as browsing the Community Market. Most games on the platform are not compatible with mobile devices, but a few are.
Valve may start a sale at any time. Normally, Steam has at least two sales per year: a summer sale and a winter sale. Winter sales normally occur in December, while summer sales and other seasonal sales vary.
Open the main window (such as another user's profile or the Marketplace). Select "Games" on the title bar at the top of the window, then "Activate a Product on Steam..." As of this writing, you cannot redeem a game key on a mobile device
Most single-player games can be played offline, subject to some restrictions. Generally, you must log in at least once, and you must be logged in when you go offline, to play a game while offline. As a practical example, this means that you can play a game if you are disconnected from the Internet while logged in, but not if you restart your computer while your Internet connectivity is still lost.
Valve accepts a variety of payment methods. As of this writing and for the likely future, this includes PayPal.
This is a common error. To fix it, open Task Manager by right-clicking the task bar. Then, find "Steam Client Bootstrapper" and end the process. In many cases, after doing so you should be able to launch Steam again.
Trading cards are similar to achievements. You collect them as you play games and can eventually form sets with them. You can display them on your profile or in completed "booster packs". They can also be sold on the Community Market.
The Community Market allows users to buy and sell in-game items, such as those players can obtain in Team Fortress 2, with money contained in the user's Steam Wallet. Users can also buy and sell trading cards and other niceties. However, games themselves cannot be sold on the Community Market.
A user is automatically set to "Away" after 5 minutes of inactivity, and "Snooze" after 1 hour of inactivity. This means that the device on which they are running Steam is not in use. A user can also set these statuses themselves.
By default, you may have up to 250 friends on Steam. You can have 5 more friends for every Steam level you have, which increases based on various community-based actions you take.