Ubiquitous language is the term Eric Evans uses in the Domain Driven Design as the language between developers and business. With this language the Business Models are build for the domain driven design solution.
With this language the understanding of the developers for whatś going on in the business is growing. It's makes it easier for developers to talk to the businness and have a common understanding.
Both, as well the business as the developer must have to agree to the terminology used by the various members of the teams.