The definition of Atonement is as follows:
The English word for atonement originally meant “at one-ment” or “at one with” like being in harmony with someone and in this case it means to be at one with God through the atonement that was made possible by the substitutionary death of Christ on our behalf. The Hebrew Word for atonement is “kipur” with the verb form being “kaphar” and means “to cover, purge, make reconciliation” and “to cover with or coat with pitch.” That last definition is remarkably interesting because the same Hebrew word used for pitch is “kaphar” and that is what the Ark was covered with. When God commanded Noah to build an Ark to save him, his family, and many of the animals from the coming judgment of the flood, he was commanded to cover the Ark with pitch or “kaphar” which is to cover, make reconciliation with, or to purge. Since the floodwaters were indicative of the judgment of God on fallen, sinful mankind, it is not ironic that God used the word “kaphar” in telling Noah to cover the Ark with pitch. Thus, the Ark is seen as symbolic of God’s salvation and the atonement or covering from God’s judgment (of the floodwaters) as seen in the pitch that Noah applied to the outside of the Ark whereby God sparred Noah and his family from the judgment of sin by an atoning, reconciling covering or cover that the pitch was known for. This is indicative of salvation being fully a work of God and not of man (Eph. 2:8-9).
And you shall offer a bull every day as a sin offering for atonement. You shall cleanse the altar when you make atonement for it, and you shall anoint it to sanctify it.Exodus 29:36 (NKJV)
But this shall be the obligation of the prince regarding the burnt offerings, grain offerings, and drink offerings, at the festivals, the new moons, and the Sabbaths, all the appointed festivals of the house of Israel: he shall provide the sin offerings, grain offerings, the burnt offerings, and the offerings of well-being, to make atonement for the house of Israel.Ezekiel 45:17 (NRSV)
Through love and faithfulness sin is atoned for; through the fear of the LORD evil is avoided.Proverbs 16:6 (NIV2011)
Notice the word atonement is only in the Old Testament. Atonement will only cover your sin and they are still there to remind you year after year of the sins in your life.
In the New Testament, through the giving of the blood of Christ, our sins are not covered. Our sins are removed and forgotten by God.