The Listing owner has to select only one category which he/she can list.
There are three primary categories of listings to chose.
There are many secondary categories which in turn may have few tertiary categories.
You should select the category ( usually tertiary category) most specific to your service facility or professional profile. It is likely to be the sub- category of any one primary categories.
Once your have selected the category, you will have the option of selecting the listing features and additional business info specific about any particular category.
There are multiple primary levels of categories.