Whether you are running a Google search campaign, Google remarketing campaign, or Facebook Ads campaign, all ads must point to a destination. There are many options out there. You could point to your homepage or a standard service or product page on your existing website.
You could custom code a landing page designed specifically for the campaign. You could use a pre-built landing page template on a platform like Unbounce or Hubspot. Or, you could point to a microsite or one-pager.