There are many different types or oregano. Many plants listed as Italian oregano in the nursery or garden store are actually marjoram. The only way to tell, that I know of, is to taste it. Oregano is spicy and numbs the tongue. Marjoram is not as strong of a flavor, but it is similar. If you really want to know that you have a specific strain of oregano, then order it from a specialty nursery that specializes in herbs.
There are many different types or oregano. Many plants listed as Italian oregano in the nursery or garden store are actually marjoram. The only way to tell, that I know of, is to taste it. Oregano is spicy and numbs the tongue. Marjoram is not as strong of a flavor, but it is similar. If you really want to know that you have a specific strain of oregano, then order it from a specialty nursery that specializes in herbs.