Configurations: contain user preferences or other application settings.
Configuration storage: makes this information permanent. The application will read the configuration at every start, but it is only stored if a user changes settings.
Key databases: are used because of these constraints. They can do fast key lookups and the keys can be structured hierarchically by defining separators in the key names. Unlike SQL databases, the key name is the only primary key; there are no foreign keys, and no query language exists.
Global key database: provides global access to all key databases of all applications in a system that wants to access a key database.
To elektrify an application: to change the application so that it uses Elektra afterwards.

Technical Concepts

Backends: A collection of plugins to be mounted. A backend typically is responsible to read and write a configuration file.
Bootstrapping: To read the mounting configuration and mount during kdbOpen().
Cascading: To consider multiple places to look for a key.
Contracts: Contracts state the purpose, functionality and requirements of plugins.
Mounting: To persistently and permanently include a backend in the global key database.
Namespaces: Allow us to have multiple keys for the same purpose and otherwise the same key name.
Plugins: The unit of implementation for a feature.

Details

Sync Flag: Marks keys that were changed and need to be written out to disc.
Null Keys, Null Values: The absence of keys or values.
pop: used in ksPop() and KDB_O_POP means to remove a key from a keyset.
delete: or abbr. del, used in keyDel(), ksDel() and KDB_O_DEL means to free a key or keyset. The memory can be used for something else afterwards.
remove: means that the key/value information in the physical database will be removed permanently.