Russell’s distinction between ways of knowing. Only the objects of immediate experience are known by acquaintance, through our direct awareness of them. Other things are known only by description, through the mediation of our apprehension of true propositions about them. For example:

“I have a headache now.” may be known by acquaintance, but

“Aspirin will relieve a headache.” can be known only by description.

Despite its apparently narrow extent, knowledge by acquaintance is supposed to provide the foundation for knowledge by description.

(Via Philosophical Dictionary)

Knowing God by acquaintance is much different than knowing Him by description (propositionally).