Yes. It is literally an animated gif.
The person you are hiring to make them should certainly understand they need to deliver an animated gif since, like all things, there is a set workflow required to produce one.
I would stay away from the term "explainer video" in this instance, which, at least to me, suggests this style: Twitter explainer video - which is a roughly two minute long introduction/explaination to an app/concept, usually animated and with a voice over (and some cheesy music).
Of course simply saying "Hi, I need an animated gif" is not going to cover it! So perhaps the following sums it up as neatly as I can think:
Suggested (micro) brief
I need a series of animated gifs, each a few seconds long, depicting
sections of my app UI in use, so that end-users can visually
appreciate how various interactions work.
One example might be selecting various values from forms and running a
I attach an example, which illustrates the length and style I require
(Then you'd attach the animated gif above)