Before we come to explain the method of wearing the Ihram it is worth knowing that the worship which is offered upon reaching Makkah is of two kinds: one is called the Haj and the other the Umrah. Haj, like Namaz, Zakat, and fasting in the month of Ramzan is an obligatory duty in Islam and included among its fundamentals. Umra, so to speak, is a minor Haj. But not obligatory, it is a Sunna. Here we should note that the pilgrims who go to Mekka with the intention that they will perform the Haj first and will not do an Umrah before it, then such a kind of Haj is known as Ifrad. And if they intend to do the Umrah first and then perform the Hajj there are two ways of doing it.
Qiran: One is that a single Ihram is worn for Umra as well as the Haj with the Niyyat (intention) that both of these acts of worship will be performed with the same Ihram. It is called Qiran.
Tamattu: If, on the other hand, the first Ihram is worn only for Umrah and it is removed, i.e. taken off after the Umrah and another Ihram is put on at Makkah for performing the Haj, then such a Haj is called Tamattu.