Candied orange zest/rind, in the simplest term, is the orange part of the orange peel boiled and candied in a heavy syrup. It is generally taken from the syrup after boiling for an amount of time, drained, and placed in granulated sugar (sometimes powdered sugar) and tossed to coat. Some recipes call for leaving it in the syrup and chilling it; this can be used for internal garnishes for desserts, like adding it to cakes for flavoring before baking. By only removing the orange part of the rind (not the white part, or the pith) you can substantially reduce the amount of bitterness that may occur.
National Candied Orange Peel Day is celebrated on May 4th of each year. The staff at National Whatever Day were unable to discover the origin of National Candied Orange Peel Day.