Tell means "to relate in detail; to give utterance to," while teach means "to cause to know something; to cause to know how." Telling requires nothing on the part of the audience. In fact, it doesn't require an audience at all. You can tell a recorder or you can tell thin air. Teaching, by contrast, requires learning. Thus, teaching requires both a teacher and a learner.
One person's "likeability" might not be another's, but if our values are similar, we'll communicate better, understand each other better, appreciate each other more and achieve better results together.