Medium only comes with a simple editor with minimal formatting options and you can push your posts into "Collections", by either yourself or by other people. With that you can create lists of articles about things that are related to each other.
I only just got into it, so I can't really say what the main focus is, but that's what I think.
I'm really not trying to hate on Medium - it looks really clean, but I'm just trying to figure out it's placement in the content publishing space.
Some of the old magazine publishers are exploiting their brands by having stables of people throwing up whatever topical crap pops into their brain, never mind quality or accuracy, so there is clearly some market for topical writing (seems to me the tendency for articles to occasionally get huge attention drives posting lots of articles).
If Medium can build a brand around having decent recent articles, more power to them (I see svbtle as the same thing, with different ideas about curation).
Their home pages (https://medium.com) states "Sharing ideas and experiences moves humanity forward" which sounds really nice, but still tells me absolutely nothing about what the platform actually is/does.