The history of WhatsApp conversations on iOS and Android remained separate from each other for a long time. This is mainly due to the various backup systems used by WhatsApp, which has made it almost impossible to transfer between them. WhatsApp has been working to change this and the good news is that new functionality is finally available for Samsung devices.
This means that if you have an iPhone and want to move to a Samsung phone, you'll be able to easily transfer your conversation history. However, you should know that the process is not yet a wireless one, which means you'll need a cable that can connect to your iPhone and your new Samsung phone, basically a USB-C cable to Lightning or an adapter. equivalent.
The good news is that this is the only obstacle, so assuming you already have such a cable or adapter, then the transfer process should be fairly straightforward. The bad news is that the process only works from an Apple phone to a Samsung one at the moment, not the other way around, and not with other devices. But WhatsApp is constantly working on ways to transfer data, so we will most likely have solutions for other devices soon.