Antlers are branching bony appendages (on deer etc) whereas horns are pointed projections of the skin on the head of various animals, consisting of a covering of horn (keratin and other proteins) surrounding a core of living bone.

Antlers
Each antler grows from an attachment point on the skull called a pedicle. While an antler is growing, it is covered with highly vascular skin called velvet, which supplies oxygen and nutrients to the growing bone. Growth occurs at the tip, and is initially cartilage, which is mineralized to become bone. Once the antler has achieved its full size, the velvet is lost and the antler's bone dies, this is the mature antler. In most cases, the bone at the base is destroyed by osteoclasts and the antlers fall off at some point (often seasonal).
Caribou and reindeer use their antlers to clear away snow so they can eat the vegetation underneath and in moose, antlers appear to act as large hearing aids. Moose with antlers have far more sensitive hearing than moose without, and a study of trophy antlers with an artificial ear confirmed that the antler behaves like a parabolic reflector.

Horns
Horns usually have a curved or spiral shape, often with ridges or fluting. In many species only the males have horns. Horns start to grow soon after birth, and continue to grow throughout the life of the animal. Animals have a variety of uses for horns; including defending themselves from predators and fighting members of their own species for territory, dominance or mating priority, they may be used to root in the soil or strip bark from trees.

----The next sentence is true. The previous sentence is false----