Yazata is bang-on correct.
EmptyForceOfChi:
The difference is this,
If you teach religion it's preaching, if you teach anything else even abstract art apparently it's teaching ^_^
Teaching religion is not the same as preaching. Preaching, however, usually describes a religious sermon or recitation.
If I stand on a stage and read of the theory of evolution I would be conducting a lecture or maybe in an auditorium.
If you stood on a stage and read Darwin's
On the origin of species out to an audience, then you probably wouldn't be teaching evolution. Or at least not apart from any teaching that Darwin does in that book.
However, it must be said that Darwin's book aims to
persuade readers of the truth of what is contained, by a process of rational argument and presentation of supporting evidence. In contrast, your average religious tract expects its readers to accept without question, based on authority rather than argument and evidence.
If I stand on a stage and read the Torah, Quran or bible I am preaching or holding a sermon.
Preaching a sermon usually involves some attempt on the part of the preacher to communicate his own beliefs to the audience, which requires more than simply reciting from a textbook. However, listeners are still sometimes expected to agree to the sermon on the basis of authority.
It is possible to teach religion. It is possible to preach science. The important difference between teaching and preaching is skillfully explained by Yazata, above.