A deniable website is a site which contents can not be confirmed nor denied. You might be able to see some of its contents, but not all of it because it’s encrypted.
Take for instance this page. You are seeing this text right now, but if you were to apply some decryption to it, you would be able to see more of it.
Would you like to see more content?
(I’ll generate a private key based on a password, first time takes around 6-7 seconds on Safari and Mobile, less than a second in Chrome & Firefox. This most likely won’t work in a native android browser...)