The style of writing is great for beginners, because it's completely focused on the outcome of each typed command, and the Vim jargon gradually accumulates:
That's good so far, what more can we say about
You have to tell it what by following with a movement command: it deletes from the cursor position up to where you tell it.
Interesting, how about some more concrete examples?
dwdeletes the word you're on, up to the start of the next word.
dldeletes up to the following character; i.e. the single character your cursor is on.
Eventually more abstract concepts are introduced, but still in the same clear style:
Text objects are another way to select areas of text. They can't be used as movement commands in normal mode in and of themselves, as they refer to regions; they may only be movement command arguments to commands that do something to regions, such as
c. They are, however, very useful.
I lied, though: they can be used directly in visual mode, which selects the region they refer to. Experimenting with this is a good way to see how they work.