You can embed standardized bits of text in one page by calling from a "Template".

Template:Templateexample

This is useful, but not earth-shattering. However, you can have templates with variables in them

Template:Templateexample2

And you can have templates inside templates, and templates inside templates inside templates.

Template:Templateexample

And you can have templates with variables inside templates with variables. It's like turtles all the way down.