Modulation

Simply understandable as change of Fundamental tone to Other fundamental tone (one key area to another key area), but still in 1 part of same song. For example the verse played 1=C then the chorus played 1=A. Example:

From above, initially keys is 1=C then after chord Dm, chord E give modulation to keys A. Then in eleven bar, after Dm – G7 give modulation to keys of C.