Using v-show directive we can toggle the presence of an element.
v-show can be used in pretty much the same was as v-if, the difference is in the way they show and hide content.
v-show will always render the content regardless of the truthyness of the expression value whereas v-if will only render the content if the expression is true. This means the v-show just use style="display:none" to show/hide the content, but it is always rendered in DOM.
Whereas, v-if will completely destroy and reconstruct the element based on the expression value.
Currently you can see some text on the page, but if enter app4.isSeen = false in the console. You should see the message disappear.
Also, if you try entering app4.isSeen = !app4.isSeen multiple times, you will the toggle display behavior with text showing, hiding, showing and so on.