You can setup different page extensions. You can make your pages URL to end with /, .html, .html or any other value. This could be easily configured in the admin panel.
Custom Block
This custom block is created in Admin Dashboard. You don't need to edit any html / php files to create new blocks. Everything could be easily created in admin panel.
You can create several types of blocks including Smarty, HTML, Plain Text or even PHP. Check Admin Dashboard / Content / Blocks management page.