Is Redux for frontend or backend?

I'm curious to know, does Redux primarily belong to the frontend or backend realm of development? As someone who's been exploring both worlds, I've come across Redux as a popular state management library. However, I'm not entirely clear on where it fits best within the broader development landscape. Could you help me understand if Redux is primarily designed for use in frontend applications, backend systems, or perhaps has a more versatile role across both? Your insights would be greatly appreciated.