Oracle breaks up the key into major and minor parts. You can think of the major part as the object pointer and the minor part as the fields in the record. So you might put a name and Social Security number into the major parts of the key and other strings like the street address and ZIP code into the minor parts. It's comparable to the way that some other NoSQL tools let you think of the value in the pair as being an object with multiple fields. Oracle just uses the term "minor key" for the names of the fields.
The serious part of Oracle NoSQL is a practical approximation of ACID compliance, the standard that SQL databases like to offer. ACID means "Atomic, Consistent, Isolated, Durable transactions," and there's a robust debate about just what this translates to in excruciating detail. Most NoSQL systems promise a different acronym, BASE, which stands for "Basically Available, Soft State, and Eventually Consistent." In other words, you'll probably get the right answer except when you don't.
There will be plenty of debate about whether Oracle NoSQL offers real ACID compliance. The promises aren't as all-encompassing as they are with SQL databases. You only get an ACID promise when you write data attached to the same major part of the key. For example, you could change the address and ZIP code of the same person and get an ACID guarantee because both parts are stored under the same major key. But you get no guarantee that changes to two separate people will remain consistent. In other words, a bank could use Oracle NoSQL to store personnel records, but not to safely transfer cash between accounts because there's no ACID guarantee that the money won't get lost along the way.
Oracle NoSQL is able to make this promise because it guarantees that one master machine will hold all of the minor keys associated with a major key. Attach any collection of fields to a major key defining a person, and all of this data will end up in the same node in the cluster. But the data from different major keys could end up on different machines, and Oracle NoSQL doesn't have a mechanism to ensure that the data will be written to both simultaneously.
You can also add replication and sharding, which Oracle calls "partitioning." In essence, you arrange the nodes in a rectangle where the sharding occurs along one axis and the replication occurs across the other. If you want more reliability and faster reads, you add more machines along the replication axis. If you want less contention, you add more machines along the partitioning axis. Oracle NoSQL handles most of this configuration for you.