When doing research, for example, this shortcut is a big help.
You highlight a word or phrase on a webpage [then hold down the shortcut keys + hit spacebar, I think ] and it will open a new page with a google search in a new window.
I've seen this done. But I don't know what keys to hold down for the shortcut.
In Safari, it should be on the right-click menu.
Select your text, right click...
1st option is a Dictionary lookup, 2nd is whichever search engine is selected in Safari prefs.
It also works in some, but not all, other apps - I presume the ones that follow the Apple guidelines most closely.
It's also available as a key-commandable Service
System Prefs > Keyboard > Shortcuts > Services
I found I had to change the default, as it conflicted with 'Show Sidebar' in Safari
