The first thing Keltham tells everyone is to please prepare Comprehend Languages tomorrow; he should test the effects of lecturing in Baseline. Which he mostly expects to not work, but value-of-information, if it does work that's great to know, and generates value over time, so better to run the experiment sooner rather than later. Value-of-information is one syllable in Baseline, by the way, just 'value-of-information'.
The classic example of a cooperation-defection-dilemma is one that, dath ilan supposes, must have been common hundreds or maybe thousands of years before the times that are remembered: Two farmers, both with almost no technology, and a small supply of not-very-heritage-optimized grains that they must both plant, and eat. Each farmer plans to eat enough seed to survive, albeit somewhat miserably, and plant enough seed that next year there will be sufficient to both eat and plant; that is all the grain that they have.
But roving bears sometimes smash open grain-enclosures and steal grain. So each farmer's options include faking a bear attack on the other's grain-enclosure and stealing some of the grain there for themselves. Not enough that the other farmer starves and becomes desperate and dangerous, but enough that the other farmer will be miserably hungry this year and also the next year, because they won't have enough grain to plant for future plenty.
You could, of course, decide that the 'bear attack' was no such thing, and steal the missing grains back. But this, obviously, starts a cycle of both farmers having to sleep with their grain, and spend a lot of time watching for attacks, at the end of which they'll both lose a substantial amount of the time they needed for planting.
If you consider each farmer's available actions, and the payoffs to both of them based on both farmers' actions, it might look like:
Farmer 2:
Cooperate-2 Defect-2
Farmer 1:
Cooperate-1: (100, 100) (30, 120)
Defect-1: (120, 30) (70, 70)
...where the labels '1' and '2' also remind you of whose payoff is whose, that is, Farmer-1 gets the first element of the payoff and Farmer-2 gets the second element. So if Farmer-1 Defects and Farmer-2 Cooperates, Farmer-1 gets a payoff of 120, and Farmer-2 gets a payoff of 30.