When selling online, if you offer a large number of kinds of products to your customers, you will want to group them in categories to help you manage it as well as help the consumers to shop easier. For example, you want to divide your products into 2 types, for men and for women, you can use a drop-down menu to do that and this is also the topic of this writing. In particular, I will show you the process of how to add a drop-down menu from the main menu on Shopify.

https://avada.io/shopify/docs/create-drop-down-menu.html