What are keyboard shortcuts and how do I use them in Skype?

You can use keyboard shortcuts to easily quit Skype, send a file, copy text and a lot more. They make it easier and faster for you to use commands that you would otherwise have to access via the menus.
https://pbs.twimg.com/media/EsujoDYXMAE4r-P?format=jpg

Key combination Action
Ctrl+Shift+Comma Open app settings
Ctrl+Shift+H Open Help in default browser
Alt+1 Navigate to recent chats
Ctrl+I Open Notification panel
Ctrl+Shift+F Search for People, Groups and Messages
Ctrl+Shift+Plus Zoom in
Ctrl+Minus Zoom out
Ctrl+Zero View actual size
Ctrl+Shift+G New group chat
Alt+2 Open contacts
Ctrl+Shift+A Add people to conversation
Ctrl+Shift+U Mark as unread
Alt+Shift+E Focus Message Composer
Ctrl+Shift+E Archive selected conversation
Ctrl+F Find in current conversation
Ctrl+Shift+K Start video call

Note: Ctrl+Shift+K will launch Accessibility Insights for Web if you have it installed. It will not start a video call in Skype.

Ctrl+Shift+P Start an audio call
Ctrl+M Toggle mute
Ctrl+Shift+K Toggle camera
Ctrl+Shift+D Launch dial pad
Ctrl+Shift+A Add people to call
Alt+Shift+J Resize camera preview
Ctrl+Shift+R Refresh the app
Up arrow after sending a message Edit the last message sent