Google has announced that their gmail service will now use secure https connections by default. Prior to this change, you had to select an option to enable https connections.

This is important because without the secure connection your interactions with gmail could be intercepted on insecure networks. This means that when you use WiFi networks at coffee shops and other public locations, people could eavesdrop on your interactions with gmail. This will not longer be a risk for when using gmail.

Read more at
Official Gmail Blog: Default https access for Gmail.