Mutamatti is an Arabic word which means pilgrim performing Hajj E Tamattu.
It is prescribed for the Mutamatti‘ (pilgrim performing Tamattu Hajj) who performed Tahallul after ‘Umrah to enter into the state of Ihram for Hajj on the Day of Tarwiyah (8th of Dhul-Hijjah) from the place where they are staying, whether they are inside or outside Makkah or in Mina. The Prophetﷺcommanded his Sahabah who ended their `Umrah to enter into the state of Ihram for Hajj on the Day of Tarwiyah from their houses.
Anyone who is staying at Mina on the 8th of Dhul-Hijjah should enter into the state of Ihram from the place where they are staying. There is no need to go to Makkah. This is based on the general meaning of the Hadith which was narrated on the authority of Ibn `Abbas(R) that the Prophet (peace be upon him) said when he specified the Miqats: And whoever is living within these boundaries can enter Ihram from the place where they decide (to do Hajj). Even the people of Makkah can enter Ihram from Makkah. Sahih Al Bukhari 1526 and Sahih Muslim 1181 
There are three types of Hajj: Tamattu’, Ifraad and Qiraan.
Hajj Tamattu Consist of the Following:
Tamattu’ means entering ihraam for ‘Umrah only during the months of Hajj (the months of Hajj are Shawwaal, Dhu’l-Qi’dah and Dhu’l-Hijjah; see al-Sharh al-Mumti’, 7/62). When the pilgrim reaches Makkah he performs tawaaf and saa’i for ‘Umrah, and shaves his head or cuts his hair, and exits ihraam. Then when the day of al-Tarwiyah, which is the 8th of Dhu’l-Hijjah, comes, he enters ihraam for Hajj only, and does all the actions of Hajj. So Tamattu’ involves a complete ‘Umrah and a complete Hajj.
The actions done in Qiraan are the same as those done in Ifraad, except that the pilgrim doing Qiraan has to offer a hadiy (sacrifice) whereas the pilgrim doing Ifraad does not.
The best of these three types of Hajj is Tamattu’. This is what the Prophet (peace and blessings of Allaah be upon him) enjoined upon his companions and urged them to do. Even if a person enters ihraam for Qiraan or Ifraad, then it is strongly recommended for him to change his intention to ‘Umrah, then complete ‘Umrah and exit ihraam, so that he will then be doing Tamattu’. He may do that after doing tawaaf al-qudoom and saa’i – because when the Prophet (peace and blessings of Allaah be upon him) did tawaaf and saa’i during his Farewell Pilgrimage, and his companions were with him, he told everyone who did not have a sacrificial animal (hadiy) to change his intention and make his ihraam for ‘Umrah and to cut his hair and exit ihraam, and he said, “Were it not that I have brought the hadiy with me, I would do what I have commanded you to do.” Sahih Muslim 1211