The phone will restart like it’s brand new. The lock screen is gone. You can now set up the device without any password.
A sub-menu appears. Scroll down to "Yes -- delete all user data" using Volume Down, then press Power to confirm.
Once the process is complete, the screen will return to the main Recovery Menu with "Data wipe complete" or a similar message at the bottom.
A factory reset deletes everything. To avoid losing data next time:
Sometimes, a simple software trick saves you from a factory reset.
Use the Volume Down button to scroll down to "Wipe data/factory reset."