What is signposting?
Signposting is the use of linguistic devices (a.k.a. signposts) that signal the structure and progression of your presentation.
Presentations should be clearly structured, and the structure itself should be clear, not just to the speaker but also to the audience.
You can use signposts to indicate, for instance, the change from the opening to the main body, give examples or to introduce the ending of your presentation.
English has a wide inventory of various types of signposts, so avoid repeating the FANBOYS (For And Nor But Or Yet So) all the time.