
Explanation:
Column-Family Data Model:
This data model supports Cassandra API. Existing Cassandra implementations can be easily and quickly moved to Cosmos DB and use column family format, which is used in Cassandra. Column Family data model is similar to key-value data model except that the items in the data model adhere to the defined schema.
Key-Value Pair Data Model (Table API):
In this data model, each entity consists of a key and a value pair. The value itself can be a set of key-value pairs. This is very similar to a table in a relational database where each row has the same set of columns. The Key-Value pair solution is supported on standard Azure table API. This Table API is primarily helpful for existing Azure Table Storage customers in migration to Cosmos DB.
https://www.red-gate.com/simple-talk/cloud/azure/overview-of-azure-cosmos-db/