What's the difference between here and hereunto?

Here

Definition:

• (pron. pl.) Of them; their.
• (n.) Hair.
• (pron.) See Her, their.
• (pron.) Her; hers. See Her.
• (adv.) In this place; in the place where the speaker is; -- opposed to there.
• (adv.) In the present life or state.
• (adv.) To or into this place; hither. [Colloq.] See Thither.
• (adv.) At this point of time, or of an argument; now.

Example Sentences:

Hereunto

Definition:

• (adv.) Unto this; up to this time; hereto.

Example Sentences:

• (1) In token whereof I have hereunto set my hand this tenth day of December, 1936, in the presence of the witnesses whose signatures are subscribed.