Understanding a Passive vs. Active sentence - Be able to delineate, manipulate, and turn an active sentence into a passive sentence (and vice versa) in both English and Latin

There are three important rules to remember here:  (1) the subject is acted upon in a passive sentence;  (2) the letter ‘r’ is the most common indicator of the passive voice in the Latin present tense system;  (3) passive verbs expect agents.  Ok, let’s start with the basics. Passive is a voice. It’s the opposite of active. Simple. I could say it also complements the “yin” to active’s “yang,” but I don’t care much to do so. Anyways, in essence, what the passive voice does is move the action of the verb backwards toward the subject rather than forward toward a direct object. Conversely, active verbs move the action of the verb from the subject toward a direct object. Thus, in principle, passive verbs do not take direct objects. In English, passive verb forms typically involve some form of the verb “to be,” such as:   “I am praised,” which is passive, vs. “I praise,” which is active.  “ we were warned,” which is passive, as opposed to “we warned,” which is active.   “they will be held,” which is passive, as opposed to “they will hold,” which is active.  Note: It’s important in English to recognize that when “be” is added to a verb form, it doesn’t always make the verb passive. The addition of a form of the verb “to be” can also make the verb continual.  Here’s how to tell those forms apart: a “be” form, combined with a verb that has a participle ending “-ing,” is active, whereas a “be” form, combined with a verb that has a participle ending “-ed,” is passive.  For example: “I am praising” which is active, vs. “I am praised, being praised” which is passive; or the active form “we were warning” vs. the passive form “we were warned.” There’s a very easy way to be certain you’re dealing with a passive form and not a continual form: if it makes sense to add “by someone” after the verb form.  Whenever you can, the verb form is passive. For example, it makes sense to say “We were warned by someone,” whereas it makes no sense to say “We were warning by someone.”  Now let’s look at how the passive voice works grammatically. We’ll start with an active sentence: “Students study Latin.” If we take the active verb “study” and we make it passive by adding the verb “to be” and adding “-ed” to the end of the verb with the result that “study” becomes “is studied,” then turn the direct object of the active sentence “Latin” into the subject of the passive sentence, we end up with the passive sentence “Latin is studied.” Notice it means the same thing: Latin is being studied. But it leaves one thing out: who is doing the studying? If you want to include that in the passive sentence, you must take the subject of the active form (“students”), put it after the passive verb (“is studied”), and append “by” to the front of “students.” The result is: “Latin is studied by students.” The grammatical term for “by students” is the agent. We’ll chat more about that later.  Notice that, while both sentences say the same thing, the action of the verb runs in exact opposite directions.  In the active sentence, it moves from left to right, from the subject to the direct object.  But when the verb is changed to passive, the action runs right to left, toward the subject and from the agent. Here’s the first sentence: “I explained the passive voice.” So, what’s the direct object (Accusative) here? The passive voice. Now, let’s make that the subject (Nominative), add a form of “to be” to the verb (in the right tense, that is) and make the subject the agent, or in layman's deal-io, put “by” in front of it. The result is: “The passive voice was explained by me.”