Everybody: Anyone who searches for your phone number can find your profile.
My Contacts: Only people who have your phone number in their device's address book (and use Telegram) can find your profile by searching for your number. (Recommended for balancing privacy and discoverability by known contacts).
2. Contact Syncing and Management
Access: Settings > Privacy and Security > Contacts
"Sync Contacts":
ON: Telegram securely uploads phone numbers and telegram number database names from your device's address book to help you find existing Telegram users among your contacts.
OFF: Telegram will not upload your phone's address book. You'll need to add contacts manually.
"Delete Synced Contacts": If you've had syncing ON previously, you can tap this option to remove any contact data that Telegram has stored from your device's address book. It's recommended to turn "Sync Contacts" OFF before deleting, to prevent immediate re-upload.
3. Blocking Users
Behavior: You can block any user. Blocked users cannot send you messages, see your online status, or see your profile picture (unless you have set it to "Everybody"). You can also unblock users from this list.
4. Username Management
Access: Settings > Username
Behavior: Setting a username (@YourUsername) allows others to find and message you without needing your phone number. This is a key privacy tool. You can also acquire collectible usernames on Fragment.