1. 1d8 = 1 8-sided die. XdY; where X is equal to the number of dice rolled and Y is equal to the number of sides of each die. I think by the time I finish writing this, it should be well enough explained.
2. Thac0 is an acronym for "To hit Armor Class 0", which basically means if you opponent has 0 armor, the need to roll at least your thac0 # on a d20 to hit him/her/it. Of course if their AC is not 0, you adjust your required roll accodringly (therefore, a negative AC is better than a positive for the defender. Ex: A is attacking B. A has a Thac0 of 10. B's AC is -2. A has to roll a 12 to hit B.) A roll of 20 is a critical hit (hit no matter what, for double damage unless prevented by a helmet or some such), 0 is a critical miss (usually the character gets a somewhat longer delay between swings after they critically miss; in AD&D stuff like weapons are broken and dropped also happens.)
3. Saving throws are rolls on a d20 required of a character to make in order to resist a certain type of force, be it magic, a dragon's breath, etc.
4. Save vs..., explained in 3.
[ 11-14-2001: Message edited by: Zerthimon ]