Your phone has the ability to connect to Wi-Fi networks, providing you wireless access to the Internet.
To connect to a Wi-Fi network, you must be within range of a wireless access point or “hotspot” and know the network key if connecting to a secure network.
The number of bands that light up on the Wi-Fi icon in the status bar tells you the approximate signal strength of the wireless network you are currently connected to.
Your phone will connect automatically to a previously joined network when it is within range. When connecting to a previously joined secure network, you will not be prompted to enter the key again unless you reset your phone to its factory default settings.
When you do not need to use Wi-Fi, turn off Wi-Fi to save battery power. The Wi-Fi widget on the Home screen lets you turn Wi-Fi on and off at your convenience. Slide your finger left or right across the screen to find this widget, and then tap the widget icon.

If you do not find the Wi-Fi widget on the Home screen, you can add the widget by following the instructions in Personalizing Your Home Screen: Widgets.