The next time you sit down to type an email or write a document for work, make a shopping list, or write out a check (if anyone still does!?), reflect on the now-automatic writing process that your body and brain complete without you even knowing it!
Your brain is working to generate ideas, organize those ideas into coherent paragraphs, sentences, words, letters... you have come up with a format for your writing, included capital letters and punctuation, put spaces between your words, and put your letters on lined paper with some semblance of organization. The language centers of your brain have retrieved the appropriate vocabulary, encoded (spelled) the words correctly, and edited your writing for grammar.
Now look at your body: you're sitting (hopefully upright with good posture!), your hand is holding a pencil and moving it to make letter strokes out of good habits. Maybe you're typing in which case your fingers are fluidly moving over the keys in even keystrokes, automatically finding the letters you need.
There's a lot that goes into writing and as adults we take for granted how everything comes together to get it all written out before we move onto the next item on our to-do list!
For kids, the writing process is not yet automatic and there's a lot to consider when kids get "stuck" or struggle to produce written work. This graphic by CALL Scotland shows a graphic of how teachers and therapists analyze and troubleshoot writing difficulties -- it's not easy to piece apart exactly where supports are needed!