AI for business means applying algorithms, such as Machine Learning or Deep Learning, to improve specific operational systems concerned with running a business. Examples include better ways to qualify sales leads, improving ad spend for online marketing or using knowledge graphs to surface contextual information, etc.
AI in the enterprise is in contrast to just regular AI organizations use to develop their products with (the intention being to make a sellable product, not improving efficiency in the back office). Examples of that would be Tesla using AI to teach cars how to drive or IBM Watson using AI for X-ray interpretation. While those applications are AI, they aren't made for running a business more efficiently – and that's the key difference.
There is, however, a growing grey area where formerly consumerized AI technologies make their way into enterprises, for example Amazon Alexa branching off an office version with Alexa for Business. In fact much of the Smart Office idea is directly derived from consumerized technologies.