Customised content in the Optional Sidebars

Please bear with me on this, I am new to Wordpress and have so far managed to understand most of what is happening, I am an experienced CSS/HTML coder (hand not WYSIWYG) I have pages and category posts on those pages For example History The Romans The Celts Food and Drink Local Recipes Vegetarian Desserts I want the Optional SidebarOne/Two/Three to display material relevant to the Category/post At the moment the sidebars display fine with advert widgets and text box widgets - the SAME output is on ALL pages However I cannot see how to make the Sidebars display different relevant material Please can you advise Many thanks