Often the best connections on Twitter are with the people you know and care about. To help you connect, your account settings by default allow others to find you by your email address. After you add a mobile phone to your account, your mobile settings by default allow others to find you by your phone number. You can change these settings at any time.
If you've let others find you this way, Twitter may suggest following you or show your public profile to others who already have your email address or phone number. People may find you through our Find Friends feature after they've imported their contacts to Twitter, in the Who To Follow section as a suggested account to follow, or on third-party services that have integrated Twitter. For example, when people receive email from you on email services that have integrated Twitter, they may see your Twitter profile and, if they’re already following you on Twitter, your most recent Tweets. This helps people you know keep in touch better with what you care about on Twitter.
No, your email address and phone number are not publicly displayed on Twitter when you let others find you by them.
No, your email address and phone number are not shared with third parties when you let others find you by them. The settings let people that already have your email address or phone number find you on Twitter by matching the address or number that they provide to your account.
To let people on third-party services find you on Twitter, a cryptographic hash of your email address or phone number may be exchanged between the service and Twitter, but no actual email address or phone number is shared. The hashing process converts an email address or phone number into a new string of text that does not disclose the email address or phone number, but allows those that already have the address or number to look up the Twitter profile of a user that has let others find them by the address or number.
To turn off the setting that allows others to find you by your email address:
If you have your phone number added to your Twitter account, you can turn off the setting that allows others to find you by that phone number through the mobile settings page. Under your phone number, just uncheck the box that says Let others find me by my phone number.