Multichannel simply means that financial services and banks must provide services to its customers through various channels such as in-branch, ATMs, call center, online banking and mobile - but they don't necessarily work together in a unified way. Simply put, each channel supplies different services and runs separately from the others.
While multichannel is focused on transactions, omnichannel focuses on interactions. Omnichannel has the customer as their central focus, providing them with a personalized message in a seamless, unified experience. This allows the customer to easily access information from any of the channels since the channels are connected to each other.