Erm... it's pretty hard to describe. It's probably easier to describe the characters. From wiki...
Blackadder though is a cynical, cowardly opportunist concerned with maintaining and increasing his own status and fortunes, regardless of his surroundings. In each series, Blackadder is an almost modern voice puncturing the pretensions and stupidity of those around him, and what might — through modern eyes — be seen as the more ludicrous and insane follies of history
The lives of each of the Blackadders are also entwined with their servants, all from the Baldrick family line (played by Tony Robinson). Each generation acts as the dogsbody to his respective Blackadder. They decrease in intelligence (and in personal hygiene standards) just as their masters' intellect increases. Each Blackadder and Baldrick are also saddled with the company of a dim-witted aristocrat whose presence Blackadder must somehow tolerate.