So I've dredged up the grammar lessons I remember, read a lot of stuff in the grammar books and on the internet, and revisited my childhood frustration with teachers who irrevocably linked words that sound alike but otherwise have no reason to be linked: "lie" and "lay," "there" and "their," "sit" and "set," "its" and "it's." My eight-year-old self thought that this linking would clutter up my mind with meaningless associations between words so paired. And it did.
Now that my mind continues, with the passage of time, to declutter itself, I find that I do not want to write a post about this topic. Just know this: The grammatically correct command to the well-trained dog who understands some English is, "Lie down."
Beyond that, I, your trustworthy grammatical guide, would have to enter into the labyrinth of transitive and intransitive verbs, subjects and objects, present and past tense, and a whole lot of other technicalities that you can readily look up. I don't have enough string for that.
I am more interested in the romance of language. Sometimes words can do things that cannot be done any other way. Sometimes words bring to mind civilizations and ideas past. Sometimes words carry within them the tune that they sing.