Making private updates in twitter. A default Twitter account is pretty much an open book:
A--Anyone (even people without a Twitter account) can access your home page and view your tweets.
B--Each time you post a tweet it appears briefly on Twitter’s public timeline for all the world to see.
C--Anyone with a Twitter account can follow your updates.
Most Tweeters are fine with this, but you might prefer a less open approach. If so, you can configure your Twitter account to protect your updates. This means your account is much more private:
A--Only people who follow you can access your home page and view your tweets.
B--Your tweets never appear on Twitter’s public timeline.
C-- People who want to follow you must send a request, and you can then either approve or decline that request.
If you like the sound of all that, here are the steps to follow to protect your updates:
1. Sign in to your Twitter account.
2. Click Settings. The Settings page appears.
3. Click the Account tab.
4. Select the Protect my updates check box.
5. Click Save. Twitter updates your profile to protect your updates.
Reference : wiley.com