The voice is the overall presence of a behind the text.
personality
syntax
diction
point of view

Personality

A person's voice reveals their identity, who they are. Voice in writing does the same. A humorous person will have a tendency to write much differently than someone who is solemn. Their choice of words and sentence structure would vary greatly thus altering the voice or personality of their writing. It is important to have voice in writing because it makes the writing unique and interesting. However, just like in life, too much personality or voice can distance your readers and hurt the overall message.

our founding fathers introduced the revolutionary idea that each person's desire to pursue their idea of happiness was not self-indulgence, but a necessary driver of a prosperous society. they created a government to defend that right for everyone.