Zoho CRM web tabs

We are looking to create a custom app for our CRM. We currently have professional edition and I went to set-up -> apps and add-ons -> zoho apps -> build custom apps. I am a bit unclear on what my next step should be? Are web tabs the same as Zoho creator? If we want web tabs we need to upgrade to Enterprise edition, i get that. But will we then need to add Zoho creator service? Looking for answers, any help is appreciated.