Google+ like Facebook allows you to update your status, create photo albums, tag things and comment on status of your friends. It has many features similar to Facebook.
However, you need to have an invitation from someone to join Google+ as the project has some issues that need to be resolved before it is thrown open to tje public.
If you have a Google or a Gmail account you can join Google+ and invite your friends too.
Here is a handbook on how to invite your friends to join Google+
Step1- Using your Gmail or Google account details (username and password) sign-in your Google+ account. Click on ‘View and edit’ underneath ‘In your circles’ option of your homepage.
This will direct you to a page where all the people known by you are organized in circles (groups) by topic like Friends, Family, Acquaintances, etc.
Step2- Click on ‘Create circle’ option and enter the ‘Circle name’ of your choice (Invites-preferred). Enter some text in an empty rectangular field (maximum 350 characters).
Step3- Enter the name of the person whom you want to invite to join Google+ in the ‘Search people’ field and click on ‘Create an empty circle’ option.
Step4- Invite more people to join Google+ by clicking on ‘Add a new person’ option and enter his/her name and e-mail address. Do not forget to click on ‘Save’ option after adding every person and tap the ‘Create a circle with _ person’ option.
Step5- Once you have created your ‘Invites’ circle successfully, place the cursor over the name of the person to open up ‘Invite people to join you on Google+’ field and click on ‘Invite’ button.
Your friends will receive a mail along with a red box which will direct them to the registration page once they click on it. Ask them to enter the details after which they will be ready to join you on Google+.