The concept of a speed run is both simple and complex at the same time. It's easy to grasp what it is, yet defining it makes for a challenge.
The essence of a speed run is this: getting from the start to the end of a computer game as fast as humanly possible. As in, as fast as possible, without any avoidable delay. Such as, say, story, taking in the scenes, enjoying the side quests or anything that isn't getting from start to finish. The faster, the better.
Separating the words "speed" and "run" makes it a tad bit easier to define this phenomena.
"Speed" means just that. Speed, velocity, motion, getting forward. Any moment wasted is a moment wasted, and if there is any way to unwaste a moment, that is the correct way.
"Run" is trickier. A run is everything that happens between when you press "new game" to when you either reach the end or give up. One might make the argument that there has to be some sort of intentionality to it for it to be a run proper, and that playing in general doesn't constitute a run per se. I'd argue that every playthrough is a run of one flavor or another, and that the only thing that differs is the skill with which it is executed.
Let's illustrate this with the most frequently used example of this blog: Deus Ex: Human Revolution. There are many possible runs to go for, with varying levels of difficulty. The easiest is the "I'm gonna beat this game" run, where the object is to beat the game, without any particular preferences. Then there are runs with various restrictions, such as not killing anyone, never being seen by anyone, not setting off any alarms etc. Or, hardest of all, all of the above. Any given set of restrictions is a "run".
(I'm not gonna lie to you. I've done that. All of it. It's a source of nerd pride. Respect my authoritah.)
Like genre participation, one does not need to know the genre to participate, only act in accordance. I.e. you're doing a particular run if you're playing in a particular way. It doesn't have to be formalized or given a name, but a run it is nevertheless.
A speed run is a very specific kind of run.
What makes these runs special is the laser like focus they have on minimizing the actual game time. Everything is repurposed in terms of seconds and minutes: how many minutes can you shave off by doing x or avoiding y? is it worth it to spend a couple of precious minutes early in the game in order to save time later on? what glitches, bugs and unintended features can be systematically exploited in order to become faster? what works?
The first things to go is story and morality, where applicable. If there's an option to do a good thing, and that option takes more time than the option to not do it, then that option is off the table. Except if you later on get a reward that speeds things up in some other, timely beneficial way. There's no right and wrong - there is only speed.
Then, everything else goes. Everything except outright cheating
It is interesting to see how something familiar be translated into a very unfamiliar context. There's absolutely no understanding for taking things slow and smelling the roses, and no sentimentality about anything. It's all rational, goal-oriented minmaxing, down to the last saved second - brutal instrumentality all the way.
The most interesting aspect of this is that this isn't limited to computer games. This is how instrumental rationality works overall, in all cases where efficiency is called for: in factories, in engineering, in middle management, in public policy review. Something that is a composite whole is reduced to one single measurable statistic, and then all efforts are put into optimizing for that one measured number. With a laser-like focus and brutal unsentimentality of those aspects of the whole that is not deemed important.
The question to ponder is: what constitutes a "run" in those cases that are not runtime computer games?