Mage/Adminhtml
module is responsible for backend functionality. Here you can find Controller & block related to each module in backend.
For Customer block, you can refer in Mage/Adminhtml/Block/Customer/
.
For Backend layout & template, you can check on below two paths:
app/design/adminhtml/default/default/layout/
app/design/adminhtml/default/default/template/
To find out which block is coming in use for particular page, You need to check particular layout file. For example to check Manage Customer
page block, first you need to refer customer.xml
file on below path:
app/design/adminhtml/default/default/layout/customer.xml
In the layout file, we need to check as per handle which block is loading like below section:
<adminhtml_customer_grid>
<block type="core/text_list" name="root" output="toHtml">
<block type="adminhtml/customer_grid" name="admin.customer.grid"/>
</block>
</adminhtml_customer_grid>