This bible verse is the best known, and very possible the most memorized, in the christian community; the source of inspiration for countless sermons.
The entire plan of salvation is summarized in it. God gave up what was most valuable to Him to give us that option of living with Him forever.
All we have to do, above all, is believe.
John 3:16
For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life.
(NIV)