As others have already mentioned, it is typically considered a separate page. Whether you choose with the slash or without is your preference. If a site is small I will typically opt for with/without the slash, but if a site is large and there are many different pages and the structure gets quite large I default to using the slash.
Not sure if the site you are mentioning is Wordpress based or not, if so there there are plugins that can help with this issue as well.