A framework comes up with predefined terms, thus giving you the ability to use these codes instead of having to create the codes from scratch.
No more tweaking of the base to make it look same across all the browsers. The CSS framework will do that.
No more adjusting of pixel widths and wondering if the sidebar has standards compliant for widgets or images.
Synergy is maintained across the website and on all web pages because the framework will remember everything that you did on each web page saving you the time and energy to try and remember specifications of each element.