As you might have heard, Sitecore acquired four51.io, a company know for it’s product called OrderCloud, a next-generation, B2B-focused commerce platform based on MACH architecture. Sitecore rebranded this into Sitecore OrderCloud.
Since it’s a SaaS tool, you can setup a free account within minutes: simply register on https://ordercloud.io to get your sandbox environment (no credit card needed :)). The getting started guide gives you a good understanding of the basic concepts.
Here are my first impressions on it after browsing through the playground environment and the API reference.