is there a browser on apple TV

No. the most recent two versions have Apps you can add to use services such as YouTube and Netflix, together with the iTunes Store and Apple Music. There is no facility to access normal web pages. I suppose in theory someone could write an app for that, but it would be rather clumsy to use. The other option is to use Screen Mirroring from your Mac or iOS device - you would handle the browsing on them but see the results on your TV (useful for sites such as the BFI Player which offer only play within a browser - I wish I could get it to work 😟 ).

Use AirPlay to display video from your Mac on an HDTV - Apple Support

you can advice they add one using their feedback channel

Feedback - Apple TV - Apple

personally I would never use it if they did the pains of attempting to use the browser in my xbox scared me for life.