Why HTML is used for Photoshop designs and pictures?
If you are making an online store then you would use Magento or Drupal or any other CMS as CMS is the best platform for making online stores. Advantage of CMS is that it provides more freedom than any other platform for managing web content.
Another advantage of CMS like Magento is that it is open source. It is free and since it is free, it would save you money. It would be cost effective to make an online store on a CMS and for this reason you would want to take advantage of open source CMS like Magento and Drupal.
The website would be designed on CMS and you would be able to use the site in a hassle free manner. You wont need any specific training on CMS to manage content on your website. CMS would make it easy for you to update the site with new products and change product information. Also you can add shopping cart to the CMS.
Problem with CMS
You would face a problem with the CMS and the problem is that you wont be able to upload pictures of the products that you would sell on the website. CMS doesnt understand Photoshop and for this reason it wont accept Photoshop designs and pictures.
For online store, you would need Photoshop help to develop pictures of your products and services. Here you can find some problem in uploading the Photoshop pictures on your CMS. After converting PSD into HTML5, all the problem is resolved.
Search engines understand markup language like HTML and for this reason CMS is designed on markup language. If the Photoshop designs and pictures can be converted into markup language, the designs and pictures would become CMS compatible.
You have to use Photoshop to develop pictures of your products but Photoshop pictures cant be used directly on the CMS. Doing so would slow down speed of website. The only way out from this problem is to convert Photoshop designs into markup language.
How conversion is done?
Conversion is a process that involves writing codes for Photoshop files. The files are broken into small files and then each file is coded in markup language. It isnt an easy job as a web designer has to sit down and write codes with his hands. For PSD to HTML5, the designer has to do coding with hands.