Magento 2 How is Layout.xml rendered to html file

Question

I have this catalog_product_view.xml in my theme layout folder.

I want to edit the html code for this part all-products-left-wrapper,

<referenceContainer name="content">
    <container name="all-products-left-wrapper" label="All Products Left Wrapper" as="all-products-left-wrapper" htmlTag="div" htmlClass="all-products-left-wrapper" before="-">    
    </container>
    <block class="Magento\Catalog\Block\Product\View\Description" name="product.info.media.image" template="product/view/mediaimage.phtml" />  
</referenceContainer>

But I have searched all over my Magento folders, I simply can't find the phtml file for this?

But on the front-end, when I look at the source code from browser, I do see this is generated <div class="all-products-left-wrapper">. So how does Magento 2 render it's .xml files to html?

Answer 1

This is a duplicate of a few SE answers (this for example), but the short answer is that default theme files are under vendor/magento and you can copy them to your theme just like in Magento 1, but there is a significant difference in naming conventions for the pathname in Magento 2.

In your example, the default file should be located at vendor/magento/module-catalog/view/frontend/templates/product/view/mediaimage.phtml

If you have an activated and applied theme (we will use Your_Theme for this example). The file can be copied to

app/design/frontend/Your/Theme/Magento_Catalog/templates/product/view/mediaimage.phtml

and then you can edit away!