Firstly: Definition of Ihram
Linguistically: It means entering into a state of prohibition. One says “a man entered into ihram” when he enters into the prohibition of a treaty or covenant. Thus, what used to be permissible for him is now prohibited.
Technically: It is the intention of commencing rites. [968] Ibn `Uthaymin says: “Whoever wears the garments of ihram without an intention has not entered into ihram. On the other hand, whoever intends rites has entered into ihram even if he does not wear the garments of ihram. However, he has transgressed one of its restrictions.” This is the position of the majority: the Malikis, Shafi`is, and Hanbalis.