You can feed deer grains, apples, hay and various feeds. You can also grow nutritional grass in your yard that deer can eat and benefit from.
Deer often are supplementally fed during late fall, winter and early spring because people don't believe that they can survive those time periods without supplemental food. You may also place a salt lick near the deer feeding area.
There are disadvantages that come with feeding deer. When you feed deer, it disrupts deer migration patterns, creates a feeding ground for predators and kills vegetation, reducing the forest's ability to protect deer in the future.