what is thac?
is it better to have a high thac or a lower one and why?
sorry about the stupid question but i am new to this die rolling stuff

Lower is better. THAC0 means "to hit armour class 0" - the minimum number which you have to roll on a die to hit a "monster" with a zero armour class. If the monster's armour class is higher (worse) than 0, the number you actually have to roll is adjusted accordingly. Check out here for an explanation of THAC0 and other AD&D terms.

Okay...detailed description.

When you attack a monster, the game rolls a 20 sided die. If the number rolled, plus any attack modifiers (attack bonuses, target's ac, etc.) is greater than or equal to your ThAC0, you hit the target.

One thing to remember is that if the game rolls a 1, you will always miss, no matter what. Also, if you roll a 20, you wil always hit, no matter what.

Of course, you only do damage if your weapon can hurt the target. Some creatures can only be hit by certain types of weapons, and others can only be hit by weapons that are enchanted to a certain degree.

thanks to both of you that definitely clears that up for me.
ill post again if i have any more questions