There's a lot more to NoSQL than you've gotten into here, which is mostly specific to document databases like Mongo or Couch. Column stores like Cassandra or HBase, for example, do use an essentially tabular metaphor and enforce schemas, although there are some important differences with what that means in a relational context. This is an excellent comparison of the major NoSQL databases that showcases the differences in their designs and uses.
Of course, the single most important thing to know about NoSQL is that unless you can articulate why you need this particular NoSQL database, you are almost certainly better off sticking with something relational :)
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