In simplest terms, what does it mean to curve marks

I haven't been able to find an online explanation I can understand

It can mean several things.

Off the top of my head....say you have a test, and the highest score is an 80%. It was a hard test. If the prof curves this way, he could then take that highest score and make it the new 100%, and base all the other grades off of that. This helps you if you got say, a 50% F and think you failed it, when after you do the math (can't be fucked to do that right now myself) you'll end up with like...I dunno, um...well, a D I think. Yeah.

Or it could involve a bell curve where only so many students can get A's, so many B's, so many C's..etc. With the C's having the bulk of the class in the middle. Say you get a really easy test and the lowest score in the class is a 90%. Well with this style of grading then that is a fucked situation, as only a certain percent of the class at the top will get an A. And that person with the 90% would get stuck with a D, maybe an F if the professor is enough of an asshole.

That's how I understand curves to work. I'm sure there are other ways.

it may be called differently. have you heard of "scaling " marks?

The only downside is you may sometimes get bellslammed and have your mark actually drop a few points.

lets say the exam is worth 100 points. but no one get 100. in fact the highest score is an 80. well to keep from looking bad teach decides to curve the marks. adding 20 points to make the 80 equal 100. this means if you got a 50 on the test, thanks to teaches curve you now have a 70. congrats you pass

there are a few different systems. one of the most common i have seen is the awards of grades based on how many people they think should recieve them. ie, the top 15 % gets an A, the next 25 % a B and so on.

also a normal distribution can be assigned to the marks, and scores boosted so the average mark is 50 % (or whatever they feel like), and grades done on population.

of course, almost all of this is done behind closed doors and not reported, so it makes it very difficult to nkow if you deserve the mark you got.

Curving refers to any of many different ways professors/teachers change your final grade on a certain assignment or test. It's done to make your final grade more accurately reflect your knowledge in the course, ideally. More practically, it keeps teachers from looking bad and students from failing.

Most of the time, curves are only necessary for the harder classes, where nobody or very few people will receive between 90-100, the traditional "A". So they are most prevalent in business, math, physics, chemistry, etc. and rarely done in arts, languages, philosophy and the like.

For example, I had one mechanics course(physics) where you could literally get half of the test right (50%), and that would curve up to a B-. That professor was a shitty teacher, so the curve allowed him to not give everyone in the class an F, and hid the fact that he sucked at teaching.

PS: Note that sometimes, a curve will be a simple algorithm that changes your actual percent grade and stick with the standard grading scale, while other times, it will redefine what percentage goes with what grade and maintain your original percentage.

http://en.wikipedia.org/wiki/Normal_distribution

Mostly, instructors just scale it linearly, though.