The Two step verification process is a feature of Gmail that allows you to add an extra layer of security to your email account. If you enable the two step verification, whenever you check into a Google account from a new place such as a new browser or a mobile phone, you will have to enter a security code, apart from your password. Thus even if a hacker gets hold of your password, he may not be able to login to your account.

Here’s how you can enable it.
#1 Sign in to your Google account.
#2 Select Account Settings from the drop down (top right corner)
#3 Under Personal Settings in Security section select “Using 2-step verification”.
#4 You will get the following screen Click Set up 2-step verification.

#5 Choose how you’d like to get verification codes in a text message (SMS) or voice call, or from an application on your smartphone. (Landline mobile/ smartphone (android, blackberry, iPhone))
#6 Complete the wizard by filling your country you live in and the mobile number.
#7 Click Send code once you have entered all the details.
#8 If you chose any of the available apps, you have to first download the app from the appropriate App store.