Most people use the 'easy' mode - in this mode when we issue multiple requests, the second request will not start until the first one is complete. This is known as synchronous execution, and this is the one we normally use. [...] In [multi] mode all requests can be handled in parallel or asynchronously. And it can be quite handy and time saving on many occasions.
He gives some code examples of how to use the library to simplify the curl connections and requests and pass the result off to a callback when it's done. His more practical example shows how to search for a set of terms on Google and return the results for output.