The main difference between freezer and wax paper is that freezer paper is opaque and coated on one side, while wax paper is transparent and coated on both sides. Recipes or craft projects may call for the use of one or the other, but you may have to look long and hard to find freezer paper at your local grocery store. Once a common item, plastic food storage bags have taken the place of freezer paper. Pick up wax paper in the aisle that also sells food storage and freezer bags.
Butchers and the personnel in the deli, meat and seafood counters in your local grocery store use freezer paper to wrap up food. Employees in the deli or meat section place meat and seafood on the waxy or plastic-coated side of the paper before folding and wrapping the item and sealing it with tape. The coated surface keeps juices from bleeding through the paper, while the outer-facing paper side allows them to write on the exterior of the package to identify it.
Some recipes call for wax paper to line baking dishes, cake pans or cookie sheets, as when you're making jelly rolls. The see-through paper contains a thin nontoxic wax coating on both sides of the paper, which helps prevent delicate baked goods from sticking to pans without shortening or oil. Parchment paper, also available in the same aisle of your grocery store, differs from wax paper in that it has no special coating, but it's used to prepare food for steaming in folded parchment pouches in the oven.
Wax paper can cover items in the microwave to keep them from spitting or bubbling while heating or cooking. You can't use freezer paper in the microwave, because the uncoated side may catch fire. But quilters use freezer paper when ironing on appliques or creating stencils for their quilted items. Freezer paper also makes a good medium when you make your own sewing patterns. For the artist, a wax paper covering over a clay sculpture in progress keeps the clay from drying out too quickly. On a tabletop, it protects the table from paint spills and more. And some crafters use it for wax-resist projects.
Do not substitute wax paper for freezer paper, because these two are not interchangeable. Each has its own purposes and best uses. If you use wax paper in the oven, verify that none of it is exposed directly to heat, because it can burn and the wax can melt if it gets too hot. Parchment paper may offer a better option inside the oven when it's rated for higher temperatures.