An update to the latest software for your Mac will mean iTunes is no longer a thing for you. In macOS Catalina iTunes is replaced by three separate apps for music, TV & podcasts.
For Apple Music subscribers the music store will now be hideen on Macs. The move away from digital downloads fits with the industry trend of revenue coming from paid subscriptions and streaming.
Your music & previous purchases will still be in the Music app and you can restore the store function in your settings. However, DJs who relied on iTunes have run into major issues due to the update. They're losing the XML file support, which is popular amongst DJs for easily sharing their playlists with other applications.
If you're curious what programs like Traktor & Serato have to say about the update you can find that here.