Alexa Presentation Language (APL)
What is Alexa Presentation Language?
Put simply, APL is a layout system you can use to give your Amazon Skill a cohesive look.
As the developer you only need to layout a message once with APL, and Amazon handles the different screen sizes automatically so your messages always look great.
It's predominantly designed for Echo devices with displays, but it also incorporates SSML for structured voice outputs.