The new features basically mirror a lot of Discord's functionality in a blatant attempt to catch up. The new Steam chat revamps how your friends list is organized, with a customizable 'favorites' section up top followed by friends grouped up in a party or by which game they're currently playing. Drag some of them together into a chat window to create a new group chat, which can be refined with settings for text and voice channels as well as member permissions.
There are a handful of other new quirks, too, like (finally!) a promised invisible mode and custom friend-request links you can email or send outside Steam. Heck, media links will even expand into appropriate little boxes, so drop all the GIFs and YouTube videos you desire. The updated features are long overdue, but there's no reason to punish yourself more by not signing up for the beta in the Steam client (Settings > Account) or by clicking here. It's free. You don't have to chat like it's 2004.