The Single Articulation Patches (also called "Singles") most closely resemble what you might be used to from other sample libraries: These patches contain a single articulation along with all applicable controls. They are tailor-made to play that one articulation and always work right out of the box.
You will find all regular articulations as Singles, but also a few special patch types like our Adaptive Legato and the Trills Orchestrator (which lets you play a trill by simply holding its interval on the keyboard.
The Multi Articulation Patches (also called "Multis") is where it gets a bit special. These patches depending on the collection feature either all samples for an instrument, or a "Longs", "Shorts" subset of them in a single patches (which, despite that name, is not a "Multi" in Kontakt's sense, but rather a very large patch. If possible a multi will unite the whole sample set of the instrument in question. In some collections (for example Berlin Strings Main) this is not possible because the amount of samples exceeds Kontakt's limits. In these cases the sample pool is grouped into different patches.
Multis allow you to load all samples belonging to an articulation into one of twelve slots (more about the usage can be found in the User Guide). Most of these loadable sample sets behave just like their Single Articulation counterpart, for example Staccato or Tremolo. In some cases, what makes a particular Single special is not available in a Multi, for example the Trills Orchestrator, or the different attack layers chosen by velocity from a Legato patch. Instead the Multi for these two example gives you individual intervals to load into slots as well as all attack styles as individual "articulations". The reason for this is the different intention of the Multi Articulation patches: While a Single Articulation patch is built to let you play a given articulation with all bells and whistles it can offer, the Multis are intended to let you build your own articulations.
There is an easy rule: If a Single Articulation patch can do it, use it. If it can't do it, open a Multi and build it yourself.
You want to crossfade tremolo with a soft sustain? Use the Multi!
You want to morph seamlessly from a non vibrato sustain to a halfstep trill? Use the Multi!
You want to switch between multiple articulation via velocity? Use the Multi!
Thanks to the power of Capsule, the possibilities are nearly limitless. Of course you can also use the multis to simply keyswitch between articulations, but that is not their main point. Complex polyphonic Keyswitches, free blending and morphing and allowing you to create your own articulations is where the Multis shine!