Templates control how the information on your pages and product pages are displayed. They allow you to reuse common code like headers, footers, and sidebars throughout your site so that you can easily edit the look and feel of multiple pages throughout your website at once.
More specifically, product templates control how the information on your product pages are displayed. For example, your product template would include fields for product title, images, thumbnails, variants, description, related products, add to cart button, vendor, etc.
By editing your product template, you can change the look of all your product pages at once. For example, you may want to make your product images larger. Or move your product description to a different location on the page. You can do all that and more via your template.
You can also create multiple product templates on Shopify. For example, you might want to display your t-shirts differently than furniture or digital products on your site. One type of product might need more photos or options than the other so it’d make sense to have different looking templates for each.
After you create another product template on Shopify, the dropdown option to choose which template automatically appears on your product edit screen. If there’s only one default template, the option is not visible.
Shopify and Lemonstand both allow you to have multiple templates for content pages. As far as I could see, only Shopify lets you have multiple templates for product pages. Being how Lemonstand is very customizable, I may be wrong about this and just not have been able to figure out how to create multiple product templates on Lemonstand. I added this to the questions page and will update this section accordingly after I confirm with Lemonstand.