createCollection() command is used to create a collection within the database.
db.createCollection() is the correct syntax. createCollection() method has parameters string (collection name) and options.
A programmer can use various options (capped, autoIndexID, size and max ) while creating a collection within the database. Each option has its own significance. For example: capped field with option "true" is used for fixed-size collection. Capped collection is always associated with max size of collection by using size field.
max field tells about the maximum number of documents can be stored in a collection.
db.createCollection("testCollection", { capped : true, autoIndexID : true, size : 5142800, max : 10000 } )
is an example.