To login to: www.Gmail.com, you need to create a Google Account. A Google Account gives you access to Google products like Gmail, Google+, YouTube, and much more. Follow this tutorial to create a Gmail Account if you don't have one.
In order to sign in to Gmail, please enter your Google Account username and password. If you are lazy to type your password again later, you can save it on your browser. In case, you forgot your password, it's easy to recover your Gmail password. There are steps to log in to Gmail.
If you have more than one Google Account (personal & business account), you can use multiple sign-in to switch between accounts without having to sign out and back in again. Follow our guide to sign in
When you use third-party app (desktop app or mobile app) to login to your Gmail Email Account such as: Sparrow app, Outlook, Thunderbird, etc... You need to use an app password to sign in. See more here
Most common problems when logging in Gmail is incorrect password. Remember that Gmail password is case-sensitive. Beware of your Caps lock key, since password characters are unreadable. In case login fails, Google will show you the error messages that tells you what the issue is and help options to guide you walkthough it. See more about: Gmail sign in problems