What does getCommands() return?

Look at the javadocs

 

What? That actually is already mentioned on that site,
"Gives the map of command-name to command-properties. Each entry in this map corresponds to a single command and the respective values are the properties of the command."

"Map<String,Map<String,Object>> getCommands()"
That would actually return a map with a string ( command name ) and their used informations like "description"
So you would call that similar to this:

Code (Text):

for(Map.Entry<String,Map<String,Object>> mapEntries : getCommands()){
    String command = mapEntries.getKey();
    Map<String,Object> commandInformations = mapEntries.getValue();
    String description = commandInformations.get("description");
    //description can be null if it doesn't exist in the map. All other informations that can be found are listed on that site. ("description","aliases","permission","permission-message","usage")
}