There are multiple TYPO3 extensions for creating online shopping portals. One of the most oldest and most used TYPO3 webshop is tt_products extension.
Aimeos is the latest in TYPO3 web shop extension. It is versatile, come with complete different UI. Aimeos is rather a integration of Aimeos webshop into TYPO3. It has very different architecture then that of TYPO3 but it integrates with TYPO3 backend and frontend very smoothly.