arangosh> db._help(); 

--------------------------- ArangoDatabase (db) help ---------------------------
Administration Functions:                                                 
  _help()                               this help                         
  _flushCache()                         flush and refill collection cache 
                                                                          
Collection Functions:                                                     
  _collections()                        list all collections              
  _collection(<name>)                   get collection by identifier/name 
  _create(<name>, <properties>)         creates a new collection          
  _createEdgeCollection(<name>)         creates a new edge collection     
  _drop(<name>)                         delete a collection               
                                                                          
Document Functions:                                                       
  _document(<id>)                       get document by handle (_id)      
  _replace(<id>, <data>, <overwrite>)   overwrite document                
  _update(<id>, <data>, <overwrite>,    partially update document         
          <keepNull>)                                                     
  _remove(<id>)                         delete document                   
  _exists(<id>)                         checks whether a document exists  
  _truncate()                           delete all documents              
                                                                          
Database Management Functions:                                            
  _createDatabase(<name>)               creates a new database            
  _dropDatabase(<name>)                 drops an existing database        
  _useDatabase(<name>)                  switches into an existing database
  _drop(<name>)                         delete a collection               
  _name()                               name of the current database      
                                                                          
Query / Transaction Functions:                                            
  _executeTransaction(<transaction>)    execute transaction               
  _query(<query>)                       execute AQL query                 
  _createStatement(<data>)              create and return AQL query