Universal reconciliation (also called universal salvation, Christian universalism, or in context simply universalism) is the doctrine that all sinful and alienated human souls—because of divine love and mercy—will ultimately be reconciled to God. The doctrine has generally been rejected by Christian religion, which holds to the doctrine of special salvation that only some members of humanity will eventually enter heaven, but it has received support from many prestigious Christian thinkers as well as many groups of Christians.
Unlimited atonement (sometimes called general atonement or universal atonement) is a doctrine in Protestant Christianity that is normally associated with Amyraldians and non-Calvinist Christians. The doctrine states that Jesus died as a propitiation for the benefit of mankind without exception. It is a doctrine distinct from other elements of the Calvinist acronym TULIP and is contrary to the Calvinist doctrine of limited atonement.
Even Wikipedia knows the difference.