This is a continuation of a series. You may want to start with the first post: Populism and Today’s Social Tech vs. Blogging
What is Micro.blog?
Micro.blog (MB) has two elements the 1. hosted blog and 2. the social network. They exist sort of separately but they are also intertwined. You have to have a blog, either hosted on MB or elsewhere, to be a member of the MB social network.

“Micro.blog is an easy way to host and share your posts, photos, and even a podcast in a way that maximizes what’s great about social networks and minimizes what’s troubling about them.”

Dan Cohen.

Now watch a 2 minute video: Welcome to Micro.blog

Micro.blog can certainly be many things to many people–possibly too many. In large part, what it is depends on what tools you’re bringing into it and how you’d like to use it.
It can be:

a web host
a Twitter replacement
a Twitter client that allows you to own your own data
a Instagram replacement
a microcasting platform
a full blogging platform
a new, well-curated community with a strong code of conduct
a customized feed reader for a new community
a syndication platform for one’s personal blog
a low barrier entryway to having your own IndieWeb-capable blog on your own domain.
a first class IndieWeb citizen with support for multiple types of posts, IndieAuth, Webmention, Micropub, and Microsub.

Chris Aldrich
Chris pretty well sums up all the things you can do on Micro.blog.
As the name Micro.blog implies the primary thing you can do on it is write short form posts like Twitter and Facebook. But you can also post long form posts just like you would on a conventional blog, just keep typing and when you hit 280 characters in a post a Title Field appears and you are long form posting – effortlessly. There is no friction or barriers between you and just writing.
Posting is easy, like posting on Twitter and the blog just auto-generates itself. You can post, “I like pizza.” You can post a picture of your cat plus a poem about your cat. You can post a 600 word essay about the Chicago Cubs. Whatever you want, however short or long you want. It’s one of the features I like the most. Posting photos is very easy on MB. There are quite a few dedicated photoblogs there.
And you can move. If you decide to move you can export all your posts and import them on a different blogging platform. This is exactly why MB strongly encourages you to use your own domain it makes moving easier.
Migrating from Twitter or Facebook to Micro.blog
What is the difference between Twitter and Micro.blog?
I was going to write a big long comparison between Micro.blog and Twitter then Facebook, but I don’t think I’m really up to the job. Which is why this post has been sitting in my Drafts bin for several weeks.
Here is the best thing to do: Micro.blog offers a free trial. Sign up and really try it for the trial period. You can set MB to cross post to Twitter so all your posts appear on both MB and Twitter at the same time. Give it a try.
At the end of the trial, you have a choice:

pay $5 per month to continue the hosted blog on MB, or,
discontinue the hosted blog, it will no longer work but the social network will still work. See below.

Even if you choose #2 you can still participate on the social network side of Micro.blog for free. Just go get an outside blog like at WordPress.com and attach the RSS feed to your Micro.blog account. Every post you make on your outside blog will also appear on MB for free. You need the outside blog to start new conversations. You can reply to others directly on Micro.blog.
Paying the $5 for easy posting is the easiest way to go. The five bucks pays for the service, keeps it free of ads and tracking and helps keep the riff-raff out. (That’s my opinion.)
But either way, if you are looking for a replacement social network I urge you to give Micro.blog a try on the free trial.