When you set up your phone, you added a Google account. If you haven't had a Google account before, this is more than just a password you set up for your phone.
A Google account lets you organize and access your personal information and files from any computer or mobile device:
Other than remembering your password, you don’t need to do much maintenance on your Google account - just enjoy the benefits of your secure, synchronized information. However, you can:
Many Google apps, like Gmail, Chrome, Photos, and Maps are pre-loaded on your phone. To learn about and download additional Google apps, read Google’s information.
If you’re having problems logging into your account, read Google's support information.