This is the third great "sign" seen by John in heaven (Revelation 12:1,3), enabling him to look forward to the glorious future after the final series of judgments have cleansed the earth.

Source:

KJV Defenders Study Bible, by Dr. Henry Morris, Ph.D.
Publisher: Thomas Nelson
Language: English
DEF 10 ISBN 0-529-10444-x
DEF 10-1 ISBN 0-529-10445-8