Yup. Storyboards are the first step in creating animation. Because it's such a slow and meticulous process, with every frame having to be created individually, animation has to be completely planned out in advance. In live action, you can try out different camera angles and stage business and film it all and then decide in editing what bits you want to use, but animation has to be "edited" in advance, in the storyboard and layout phase. Storyboards are how you determine the shots and angles and timings you want to use before you animate. Basically the same role that storyboards play in creating special effects shots -- a way to save time and money by locking down in advance just what you need to create. Many animators, like the Pixar staff, actually "write" their movies in the storyboard phase, starting with the visuals rather than with the script. Although Filmation worked script-first.
And as Maurice says, Filmation relied heavily on its stock system, in which they created a catalog of stock character poses and movements that could be pieced together to create the animation more quickly and cheaply than if they had to be newly drawn. Or if they did need to animate a new character, they could trace the movements from a stock shot of another character, so you'd see a lot of recurring motions over and over (although Filmation hadn't started using rotoscoped movements, i.e. animation traced from live action footage, at the time of TAS, except for one or two rotoscoped shots of the Enterprise in motion from the title sequence). They worked out their stock system meticulously so that storyboards and animation could be constructed quickly and efficiently, since time and money were at a premium.
Lincoln Enterprises, Roddenberry's memorabilia company, used to sell TAS storyboards along with TOS and TAS scripts. Decades ago, I bought the script and storyboard of "The Eye of the Beholder," partly to see how the storyboards were done, and partly because Alan Dean Foster's novelization of that one changed the ending, and I wanted a reference for the original ending.