In Sitecore SPEAK is an acronym for: Sitecore Process Enablement & Accelerator Kit
Super Quick Overview of SPEAK
SPEAK is an application development framework for use within Sitecore. It's intended to build small applications / tools for business users & marketers that act as a natural extension of Sitecore.
SPEAK accomplishes this by providing pre-built components meant to accelerate development and provide a consistent UX across the envorinment