The Greeks used several different words to distinguish aspects of what today we call wisdom. This includes a distinction between practical wisdom (Phronesis) and ultimate wisdom (Sophia). Prudence—knowing what to do—is similar to practical wisdom.
In modern English, prudence has become increasingly synonymous with precaution. In this sense, prudence names a reluctance to take risks, which remains a virtue with respect to unnecessary risks, but when unreasonably extended (i.e. over-cautiousness), can become the vice of cowardice.
Wisdom, rather than prudence, is featured in the list of candidate virtues in this course because of its greater scope. Study that page for a more complete treatment of the virtue.