'concluder') is the last person called up to the Torah on Shabbat and holiday mornings: this person also reads (or at least recites the blessings over) the haftarah portion from a related section of the Nevi'im (prophetic books).
On Jewish holidays and certain special Shabbatot, there are readings from two or more Torah scrolls.
The maftir portion for the Festivals and for Rosh Chodesh that occurs on Shabbat comes from the appropriate paragraph in Numbers 28 or 29, describing the sacrifice for the day.
The maftir portion for Shabbat during Chanukah comes from Numbers 7, describing the dedication offering of the Mishkan (Tabernacle during the wilderness journeys) corresponding to the day of Chanukah where Shabbat occurs.
Shabbat Chanukah and two of the special Shabbatot (Shekalim and HaChodesh) sometimes coincide with Rosh Chodesh.