Well, It does depend on which kind website or project you want. Like we talk about Shopping-Cart then X-Cart would be great choice. X-Cart is an open source shopping cart platform. It is one of the speediest internet business arrangements available, that is extremely adaptable, engineer cordial and accompanies inbuilt highlights'- Cart is an open source web-based business platform that empowers clients to process orders, oversee stock, and use each part of a webshop.

X-Cart enables clients to process online installments without trading off delicate information. X-Cart is perfect with numerous installment entryways and interface. The online merchant can acknowledge both credit/platinum cards and web based keeping money exchanges on their online store when clients checkout. Want to know more about X-Cart and what are the benefits it provide. I would suggest to look out this article for sure.

The answer is always "it depends".

If you care about paid support and having the most features, Magento is probably for you, but you compromise in extensibility, since the learning curve for development is steep. Magento also has the reputation of being slow.

On the other side, if you can compromise on features in order to gain development speed, OpenCart is the best choice, the project was refactored recently, so most of the codebase is clean and consistent.

Finally, if you prefer a middle ground (ie. a not-so-steep learning curve for development, a bigger set of features than OpenCart and better performance than Magento), PrestaShop is what you should explore.

At the end of the day, you can't just "learn an e-commerce framework", you should pick the tool which helps you better with your particular needs.

Drupal provides E-Commerce (site/shopping cart functionality) capability. The Open Source CMS is generally well maintained.

Thank you very much... I really appreciate your answers...

I agree that Magento is the way to go when getting started. There's also OpenCart, not as widely used but can provide a different perspective on how e-commerce can be built. I would stay away from Woo Commerce, I try to avoid anything Wordpress just because I don't trust it. I've worked on from-scratch .NET e-commerce sites, Magento, OpenCart, and Demadware.
You probably don't want to get into Demandware just yet, but if you do, the need for skilled Demandware developers exceeds the supply currently.

Magento is probably the most popular.

As with everything else, there is no best one of anything. It's what gets the job within the time and budget.

Shopify is pretty popular, as well as any number of other hosted cart systems.

Or - learn to write your own. Carts can be pretty simplistic to very complex pieces of software. Learning how to build one will teach you a lot about forms, transactions, CC processing, etc...