What is epigenetics?
Epigenetics is everything that happens to the DNA (without actually changing the sequence of said DNA) that determines what can be transcribed and how accessible the actual DNA is for transcription and, in turn, what proteins can be made. The epigenome is flexible and changes with environmental changes. (In no way mutations, that would be a change in the DNA sequence itself)
Examples of epigenetics include methylation, acetylation, histone modifications, inhibitor proteins and everything that cause genes to turned off (not transcribed) or on (transcribed). Everything that happens to the organism as result of these genes being turned off and on is also called epigenetics. Examples of this included twins with identical DNA being different or having different feature. This also is seen with mice with identical DNA.