Computers these days usually have some way to let humans search for stuff. Most of them present the results in a long list for the human to navigate. But depending on what you're trying to do, that might not be the best or even a reasonable interface to use.
Let's think about movies for a bit. Imagine you're looking for movies starring Jet Li. You might use some computer interface, type some terms like "Jet Li", and it might present a list of movies he starred in. This is searching, and a list of search results is a completely reasonable result to get here, you might care about any of them.
Now imagine you're instead looking for the specific movie called Hero (from 2002 and starring Jet Li). This is a different kind of activity I call summoning: you know what you want and you want it to be here, now. You don't care about other movies with Jet Li, or other movies called Hero. Being presented a list containing all those movies is now an obstacle that the computer is putting in your way.
Of course the computer cannot know what we want to summon so something like a list seems like a necessity, but having to find the thing we want from that list means that we are lacking affordances to be specific enough about what we want.