A hacker has been able to obtain passwords for 5 million Gmail accounts. The entire list was then posted onto a russian bitcoin forum. Since the attack, the list has been taken down.
Whilst there was no evidence about any Gmail servers being attacked, it seems as if the usernames and the passwords were leaked.
To check if your password was one of the leaked, use this tool to check if your Gmail account was in the list.
With that being said, I would strongly advise that you change your Gmail password immediately. Additionally, if you use the same password on other websites, I would go and change the passwords for those websites right now. This is because if a hacker is able to access your email account, then they have the keys to the kingdom.