Can you please explain the string theory in layman's terms

I recently watch a video of Dr Michio Kaku on the string theory, so can you please explain the string theory in layman's terms?

[For a layperson's treatment, I suggest "The Elegant Universe" by Brian Greene. I believe Kaku's book, "Hyperspace" also treats the same subject, as does "Warped Passages" by Lisa Randall.]

We used to think of elementary particles as point particles, infinintely small in size.

At very short distances, uncertainty causes vacuum energy to get very large, which would cause the creation of large quantities of virtual particles, leading to what's referred to as a "quantum foam." Also, in trying to combine quantum mechanics and general relativity, infinitely small particles and distances causes combined models to fail due to non-renormalizable infinities. [Yeah, I know, there are a couple technical terms in there. Let it suffice to say that infinitely small particles caused problems in the physics.]

So, the hypothesis was made that all particles have a non-zero size, each consisting of a very short (though not infinitely short) "string" of energy. The strings also vibrate, with various vibrational patterns resulting in the fundamental particles we see (leptons, fermions and gauge bosons). Since the "strings" have a finite size, the infinitely small distances don't occur, so the theory doesn't encounter the problems.

At this point, the "M-theory" posits a total of 11 dimensions - our three spatial dimensions, time, and seven other spatial dimensions that provide the strings the vibrational degrees of freedom to result in the particles and interactions that we observe in the Standard Model, quantum mechanics, and general relativity.

There's too much information to post in one YA response. I found a good site for a detailed explanation in layman's terms. Here is an excerpt: "Think of a guitar string that has been tuned by stretching the string under tension across the guitar. Depending on how the string is plucked and how much tension is in the string, different musical notes will be created by the string. These musical notes could be said to be excitation modes of that guitar string under tension.