Slide rules , used before the popularity of pocket calculators

what exactly did they do , was it multiplication tables only , or a lot more

Slide rule could do much more than multiplication. My father used one when he was studying engineering and I've spent a lot of time playing with it.

Along with Multiplication/Division, they can also do Roots/Powers, Logs/Exponents, and even Trig!

I'd encourage you to read the wiki article, if you're interested: http://en.wikipedia.org/wiki/Slide_rule