Was the language used in Shakespeare's plays commonly used among people at that time in normal speech? I know that iambic pentameter was commonly used in formal, pre-prepared speeches at the time, but was the vocabulary and structure of normal speech similar to that shown in Shakespeare's plays? I ask this because I do not understand sentences in his plays from time to time, even when they were meant to be comedic. However, someone told me that the jokes he told were very popular and well-understood at the time. Does this mean that they were more educated than us in the English language?
The reason you can't understand some of his jokes is that words are pronounced differently today, so the puns are a lot harder to hear.
Another reason you can't understand some of his jokes is that slang is different today, so some words that had slang meanings don't anymore.
And still another reason is that some of his jokes were very subtle – some actually only make sense if you know French – so that most people in the audience didn't understand them, and Shakespeare probably didn't intend them to.