This step is not 100% necessary but it’s highly recommended to do this step because macOS Catalina might not be compatible with VirtualBox and for this reason, it might cause problems during the installation.
Step 3: Install & Update VirtualBox Extension.Download Oracle VM VirtualBox for Mac - Cross-platform, free and general-purpose comprehensive virtualization software for x86 hardware, designed to be used for desktop, server or embedded devices.But with virtual box, you actually have macOS on a Windows PC. Windows, macOS – which one do you want to use today? On a traditional setup, you’re stuck with one or the other. VirtualBox is a general-purpose full virtualizer for x86 hardware, targeted at server, desktop and embedded use.For a thorough introduction to virtualization and VirtualBox.