Free for everyone: the News feed, the public guides, the professional directory (listing is free), and booking a professional.
Premium adds the paid features of the app, such as starting a free-form direct message to a professional and the other premium tools shown on the paywall in the app. Premium means any active subscription, whichever platform you bought it on.
Booking a professional does not need a subscription. Messages inside a booking conversation are free for both sides.
If a feature needs Premium and you do not have it, the app shows an upgrade screen instead of the feature. Nothing is deleted when you are on the free tier.
See the price ladder for what Premium costs and how to cancel.