A doubt...

A doubt…
Why when I make a stroke (line, pencil, circle, line …) I get the message to apply stroks?

¨You have added a stroke to the drawing but it will not be visible unless you activate. Show strokes from the view menu¨¨

Says the message.
I do not know what it is, I do not know how to remove it

Hit the K key:
https://docs.toonboom.com/help/harmony-14/premium/drawing/draw-stroke-tool.html?Highlight=Show%20strokes