Presenter
A similar term is master of ceremonies (MC, emcee, or host). The main use of the term 'presenter' is on television, where the presenter introduces other speakers, and introduces program sections. The role is similar to narrator, who talks over visuals ("voice over")  or plays a main role in the program. A presenter does not have to be an expert on the content of the program, but a narrator or commentatior is often an expert.