Don't get lost when creating a map.
A value must be supplied for each key.
The size is the number of entries.
You can look up the value for a given key.
Maps can be used as functions to do lookups.
And so can keywords.
But map keys need not be key words.
You may not be able to find an entry for a keyword.
But you can provide your own default.
You can find out of a key is present.
Or if it is missing.
Maps are immutable, but you can create a new an improved version.
You can also create a new version with an entry removed.
Often you will need to get the keys, but the list is undependable.
You can get the values in a similar way.