- "groups representing (musicians)" from the article is, in this case, almost certainly referring to Performing Rights Organizations (aka PROs). The PROs are groups like ASCAP, BMI, and SoundExchange who manage the business of collecting and distributing royalties to artists. When you make a public performance of a work, or when you broadcast it in some way, you're required to obtain license from one or more of these PROs and report your usage of the work to them. They then determine what the artist is owed based on your usage.
- big service providers in the industry, like Spotify or Pandora, can make "digital direct deals" with labels and content suppliers. This lets them skip parts of the process of reporting their royalties to PROs, and instead they negotiate and pay the record label or content supplier directly. A direct license like this is typically also required if you'll be offering downloads of tracks, not just streaming broadcast.
- the biggest/best change on the artist side is from the Allocation for Music Producers (AMP) part of the collection of bills passed here, which officially recognizes producers for their contributions to a work and makes them eligible to receive royalties
- the biggest/best change on the steaming provider side comes from the Music Modernization Act (MMA) part of the collection, which introduces the concept of a blanket mechanical license. Interactive streaming (think on-demand usage where the user has lots of control, not radio-style usage where the user has little to no control) requires a streaming mechanical license, and up until this point, these licenses have been cumbersome to get - you don't get one by default, you have to request one specifically for each track you want to play from the copyright holder, and the streaming provider themselves is responsible for trying to track down the rights on their own. Clearinghouses like the Harry Fox Agency try to simplify this process and provide tools for automating it, but, it is clunky at best. The MMA makes streaming mechanical licenses much more like a noninteractive statutory license, where no pre-approval is required for use as long as the streaming provider is properly registered with PROs and promises they'll record their usage, report it properly, and keep some money on-hand for the eventual royalty bill.
I don't have much opinion on the parts of the legislation that relate to copyright for pre-1972 works.
In short: it should be easier to get paid if you're a music producer, easier to get paid if you're an artist whose work is being used by interactive streaming services but you aren't big enough to be covered by a supplier or major-label direct license, and the barriers to entry for a service who wants to provide interactive streaming just got a little lower on the licensing side.