To start I will repost some of an answer I have previously posted, which will explain what evolution is:
Evolution is simply a process of change. It is a change in trait values of populations over time. It results from four mechanisms: mutation, migration, drift, and selection.
"Evolution means change, change in the form and behaviour of organisms
between generations. ... When members of a population breed and
produce the next generation we can imagine a lineage of populations,
made up of a series of populations through time. Each population is
ancestral to the descendant population in the next generation: a
lineage is an ancestor-descendent series of populations. Evolution is
then change between generations within a population lineage." - Ridley,
Evolution depends on the inheritance of information from the ancestral population to the descendant population. Much of the time we talk about information in the form of genetic variation, the information contained within the DNA. However, more and more we are realising that other forms of information transmission can occur, including epigenetic effects, and that these can contribute to evolution.
"Epigenetic modifications are a bit like ornaments on a Christmas
tree; the tree (the DNA sequence) is still the same, but the
decorations (epigenetic modifications) change how it's perceived." ...
"Over the past few years, several studies have compared the epigenetic
modifications of our genome with that of other great apes, leading to
an emerging picture of the importance of epigenetics in our recent
evolutionary history." ...
"The role of epigenetics in evolution (particularly primate evolution)
is an active and exciting area of research..." - Nature Scitable