`渊博` is a formal and very positive term. It is used in situations where you want to show great respect for someone's intellectual depth.
Praising Experts: It is commonly used to describe professors, historians, scientists, and other respected experts. For example, “My history professor's knowledge is truly `渊博`.”
In Written Language: You will frequently encounter `渊博` in book reviews, academic introductions, formal speeches, and biographies.
Common Collocations: It is often paired with nouns like `学识 (xuéshí - learning, scholarship)` or `知识 (zhīshi - knowledge)`, as in `学识渊博 (xuéshí yuānbó)`, which is a very common and elegant four-character phrase.
Formality: You would not use `渊博` to describe a friend who is good at video games or a clever child. It is reserved for serious, academic, or profound knowledge.