The Function of Saving Throws

An excellent explanaion of Saving Throws by The Man in the Funny Hat:

1E save categories are a combination of the SOURCE of the effect being saved against and the effect itself, then it looks at your class to determine what your chances to avoid/mitigate those effects are. Rate of improvement in any given category for a class tends to be a jumpy and irregular. Adjustments to saves are very few. 3E doesn't care what the source is - it looks only at the end effect, then it assigns all effects into one of three categories. There are only two rates at which those categories can then improve, good and poor. All classes have one good save, one poor save, and then one which will either be one or the other of those. At low levels your governing STAT will be the biggest factor in determining your chances of successfully saving in those three categories, and only at mid-higher levels will your class be the bigger factor. Other adjustments to saves from protective spells, items, Caster level/spell level of the source, and specific class features are numerous and outweigh both stat and general weighting due to class.

1E is actually simpler, has few adjustments (look up the number and roll), but it's also irregular in progression and generally idiosyncratic/not-very-intuitive. 3E, though it uses fewer categories and is superficially more intuitive, is actually deeply more complicated and rather strongly de-emphasizes class as the determining factor of success in favor of ability scores, items, and a wide variety of adjustments.

Key to understanding saving throws in D&D is understanding their origin of the save in wargaming. The effect being saved against is first and foremost looked upon as a foregone conclusion. Explosion goes off next to you - you're dead. Dragon breathes on you - you WILL take X damage. Spell is cast upon you - the effect WILL manifest. For spells, it doesn't even matter what the level of the caster is or what the level of the SPELL is. The chance to save is based on the victims class and the type of effect. The saving throw is then granted as a last-ditch attempt to either reduce the severity of the effect or perhaps just avoid it altogether. AD&D says, "The precise reasons why your save is set at the level it is aren't even all that important since it's all about what class your character is." 3E looked at things rather differently. The effect being saved against is NOT really a foregone conclusion. The whole process is a much more fiddly determination of success in a direct contest between caster or item and the target. Caster level/spell level sets the initial chance of success, THEN it's adjusted a zillion ways by the category of the final effect, the class of PC, his defensive spells, skills, items, circumstance bonuses, etc. etc., yada, yada, yada.