what is an api key used for code example

Example 1: key characteristics of rest api

REST is stateless, therefore the SERVER
has no state (or session data)
With a well-applied REST API, the server 
could be restarted between two calls as
every data is passed to the server
Web service mostly uses POST method to
make operations, whereas REST uses GET
to access resources

Example 2: key characteristics of api

-REST is stateless; therefore, the SERVER
has no status (or session data).
With a well-applied REST API, the server
could be restarted between two calls, 
since all data is transferred to the server.
-Web service uses POST method primarily
to perform operations, while REST uses
GET for accessing resources.