pushes up glasses and clears throat (rant, sorry but not sorry)

Actually proper ERP requires some amount of set-up (whether character sheets that both look at or a short discussion or both), the conceit that people are playing characters (sometimes even in third person) whereas cybering is kind of spontaneous and first person, based purely around the direct imagination of things being done to you the person and you doing things to the person you're typing at and rarely gets above a couple sentences per reply and doesn't tend to take place outside of the immediate realm of the possible such as one party's home or some other mundane and immediately accessible location.

Sexting IMO is just cybering with the added strong likelihood that media (visual and/or audio) of one or both parties is exchanged during the act to further it and the strong likelihood that both parties know each other in real life.

The difference between erotic roleplay and cybering is like the difference between your partner just coming up to you and starting to stroke your thigh while touching themselves and both of you agreeing an hour ahead of time to a pirate-themed dress-up occasion where you put effort into speaking like one between dirty talk and maybe use a prop or two before getting to the sex while remaining in-character.

In some cases I'd argue it's even more abstracted as not all people ERP purely for the purpose of immediate/imminent sexual gratification or amusement (some use it for practice writing for instance or to explore some kink or concept like a collaborative 2-person romance novel whereas cybering is pretty shallow and let's be honest focused on the immediate sexual act and fulfillment without much consideration to anything else)

A lot of people who talk of ERP are doing laughably disguised cybering.

-signed, a frustrated roleplayer tired of people who think "I put on my robe and wizard hat, I stroke your thigh, you moan" is the same as actual roleplay (even of the erotic variety). There are people who ERP to get off no doubt, it's quite common I'm sure but it is just the same a writing and creative roleplay endeavor whereas there's little creative thinking or ROLE-playing behind writing how you're pumping and going for broke with someone without context, story, setting outside of the reality you inhabit and as in your head yourself not a character. You're role-playing in that situation in the same way you're acting when you behave as yourself with others, you're acting as yourself so no one could really call it that or call you an actor of any skill or suppose you doing it lends itself to furthering your acting ability.