The shortcut Ctrl+K is to create or edit a hyperlink. Please see how to add a hyperlink.
Step 1: Click any cell in the worksheet;
Step 2: Press and hold the "Ctrl" key from the keyboard, then click the letter "K";
Step 3: Insert the hyperlink in the window, for example, type the website "https://excelnotes.com/" in the address box;
Step 4: Click "OK" to create the link.