BlackBerry Bold 9900 - Specifications

The operating system you use (like iOS, Android™ and Windows Phone) will depend on your phone.

The size of your phone's internal memory will determine how many pictures, videos and music tracks you can store on your phone. Some phones also come with a memory card slot so you can increase the memory.

Screen sizes are measured diagonally. The bigger the screen, the better the viewing will be when you're browsing the web or watching videos.

You can make calls, send texts and browse the internet on a 2G network. If you're looking for faster web browsing, you might want to look at 3G-enabled phones.

This is where in the world your phone can be used. Some phones can be used worldwide, while others are restricted to the UK or Europe.

If your phone's Wi-Fi enabled, you can connect wirelessly to the internet when you're in a Wi-Fi hotspot (including airports, restaurants and train stations).

Generally, the more megapixels your phone's camera has, the sharper the image will be.

If your phone's got an LED flash, you'll be able to take better photos in dark conditions. And with a dual-LED flash you'll get an even clearer image.

The operating system of your phone will come with its own application store - where you can download apps and games to your phone (some of them for free).

BlackBerry Messenger (or BBM) is an instant messaging service for BlackBerry users. It lets you send real-time messages, share pictures and even show your friends what you're listening to.

There are different types of email you can get on your phone. You can keep up-to-date with accounts like Gmail, Hotmail and Yahoo! - and with push email, you'll get your messages straight away.

Content Control stops customers under the age of 18 from accessing inappropriate content. This can be removed.