<Switch> returns only one first matching route.
exact returns any number of routes that match exactly.
For example:
<Switch>
<Route exact path="/animals" component={Animals} />
<Route path="/animals/fish" component={Fish} />
<Route component={Missing} />
</Switch>
<Route path="/animals" component={Order} />
If the Missing component was not inside a <Switch>, it would be returned on every single route.
With exact, the “/animals” route will not catch every route containing “/animals” such as “animals/fish”.
Without exact, the “/animals/fish” route will also return the Fish component for “animals/fish/cod”, “/animals/fish/salmon”, etc.
Being outside the <Switch> statement and without exact, the Order component is rendered on every path containing “/animals”.
Usually, if you’re not using exact you would use a wildcard, so you don’t return random pages.