Prophet Muhammad (pbuh) performed extra prayers voluntarily in addition to Fard prayers.
These prayers are called Sunnah prayers. It is optional.
Prophet Muhammad (pbuh) always prayed two Rakaat before the Fard of Fajr and three Rakaat after the Fard of Isha even when on a journey. The one, three, five, seven, or nine Rakaat after Isha are called Witr (odd number).
The Sunnah prayers are as follows:
Fajr 2 Rakaat before Fard.
Dhuhr 4 Rakaat before Fard and 2 Rak’ahs after.
Asr 4 Rakaat (less recommended) before Fard.
Maghrib 2 Rak’ahs after Fard.
Isha’ 4 Rakaat (less recommended) before Fard
2 Rakaat after Fard.
1, 3,5,7, or 9 Rakaat of Witr.
The Sunnah prayers are normally offered individually and no Adhan or Iqamah is needed for those extra prayers.