Regular WhatsApp is designed for friends and families to stay in touch, chat, share images, videos and generally be social with each other either on a one-to-one basis or in groups.
WhatsApp Business has been designed for businesses to connect with customers in a similar, but more formal and controlled way. While the interface is the same for the end user (businesses can send videos, photos, links etc. too), businesses must first create a WhatsApp business profile, get verified by WhatsApp and obtain opt-in from customers before they can send any messages.
Also, business messages for WhatsApp are template driven - any template used needs specific WhatsApp approval before content can be sent. This strict WhatsApp business account verification process helps builds trust and security in the community, ensuring customers feel safe in the knowledge that they're chatting with a genuine business rather than being spammed or defrauded.