Google now incorporates things such as your search history and your emails to provided a customized start page.
So if Google knows you live in Atlanta, GA it will show you the weather for Atlanta. If you have a flight booked to San Francisco, you will also see the weather for your destination and confirmation of whether your flight is on time - this happens automatically if the flight confirmation went to your gmail account.
If you search for an address or store on your desktop computer, Google Now on your phone will be aware of this and will offer directions. If you have an appointment at your Dentist in your Google Calendar, your phone will remind you, letting you know what time you need to leave to arrive on time taking into account current traffic conditions.