Hyvä Theme is a frontend framework created by Willem Wigman as an alternative to the LUMA stack. It aims to improve website speed, performance and reduce development costs compared to other solutions like Magento's default themes or Adobe's PWA Studio. Some key advantages include faster page loads which improve SEO and user experience, higher conversion rates from reducing load delays, lower development costs through simpler code, and support from an active developer community. The theme also offers flexibility, allowing stores to easily switch from other themes like the default Magento themes.