now i keep hearing "diceless system(s)" and i do not know what it means.
Usually, it means no randomizer is involved in resolving challenges.
if it is diceless is it actually a system? isn't that just cooperative storytelling without any randomness?
Removing randomizers is not the same as removing the system. A resource management system, for example, can be very intricate andn complex, yet need no randomization. It would work something like this:
I have a Warfare skill of 8 and my opponent has a Warfare skill of 10. When we go at it, my GM tells me, "Your opponent slaps your weapon away without effort and nearly nicks you in the exchange."
Clearly, this guy is better than me, so it's time to use some of my resources. I expend a few points of my War Aura and now I have a Warfare skill of 11, compared to my opponents 10. Maybe certain conditions can even give me some free points to throw into warfare (if my Intelligence is greater than my opponents, for example, maybe I get free Warfare points equal to the difference during the fight). Perhaps tactics can provide free Warfare, as well.
With diceless resource management, then, the goal is to use as few of your own resources to defeat your opponents or overcome challenges as possible, so that you'll have some juice left when it comes time to go toe-to-toe with the Big Bad Guy.
Some diceless systems rely on simple comparisons between skills and difficulties to resolve challenges, with a system of modifiers based on how a problem is approached. In Amber diceless, a combat example plays out showing how a character with a higher endurance can win a fight against a foe with superior warfare by wearing his opponent out.
Without resources to manage, however, this can be trickier for the GM, who has to adjudicate whether or not specific tactics provide any sort of bonus. It can get messy, but certainly no messier than your average d20 rules argument ("But the xill has FOUR ARMS, man, he HAS TO BE A BETTER GRAPPLER!").
In my experience, diceless games work better when there is a level of assumed competence and heroes only need to exert themselves when they're being, you know, heroic. The lack of a randomizer puts the focus on the character and the action she's attempting to perform, not on the whirling polyhedron of doom that will determine her success or failure.
Properly designed diceless games reward players (and their characters) for shrewd resource management and good tactical play. In the diceless Marvel Universe RPG, for example, tactics seem to be much more important during combats than in many other superhero games, where the most important tactic is often how you design your HERO and what your dice do to you.
From my non-playtest viewpoint, that's because the MURPG is so heaviliy dependent on the resources of your character. You may need to start a delaying tactic to build up the energy you need to really put the whammy on the bad guy, or you might want to let that punch knock you out so you can lie safely on the floor and regain energy for your dramatic return to save the day at the end of the fight.
The biggest difference between the random and non-random games, however, is probably the decision making process. A character normally succeeds because the player decides to expend the necessary resources to guarantee a success, or because the character is simply good enough to succeed at the task without effort. In a random game, however, even relatively trivial tasks can be shut down by a bad die roll and the impossible can be achieved through a really lucky roll.
Both types of system have their strengths and weaknesses, though I strongly prefer diceless play for very powerful or competent characters, to avoid the anticlimactic, "I rolled a 1." feeling.

On the other hand, I really like diceless for grittier, lower-powered games, where chance is a real factor.
Sam