BIM is an acronym describing digital design, construction and facilities management in the construction industry. "B" stands for building of course, "I" for information and "M" is not clear yet but it may be interpreted as Modelling or Management depending if you are designing or managing the project.
However the National Institute of Building Sciences in the United States put some light on this subject stating that BIM is:
“A digital representation of physical and functional characteristics of a facility… and a shared knowledge resource for information about a facility forming a reliable basis for decisions during its life-cycle; defined as existing from earliest conception to demolition.”
As the above definition didn't help us at all, we decided to look through some RIBA publications. That was even more confusioning, we found out that anybody can say what they want about BIM.
On our side we put a lot of effort in pursuing the perfect BIM definition and now we are pretty confident in saying that BIM is a multidisciplinary approach to the design, construction e management of a building (or infrastructure). Various disciplines are involved in the design of a building, such as architects, structural engineers, mechanical and electrical engineers. All of them are working on the same digital model. In this way everyone involved must work and collaborate together with the same standards. If one discipline fail to deliver his package the team fail in delivering the project to the client.
All seem pretty amazing but, as Mr D. Tail is trying to explain us, the theory may be different from the practice.