Normal computers are dumb. Sure, they work well for calculating spreadsheets and word processing, for complex engineering applications, secure financial transactions, fast information retrieval and computer games.
But all these activities happen mostly inside the computer (or inside a computer network) and are controlled by us through simple interfaces such as keyboards, mice and touchscreens. We use these simple interfaces because they are easy for the computer to understand.
Put a normal computer in the real world – to understand speech in a noisy office, to recognise you in sunglasses or after a radical haircut, to read text and actually understand it well enough to answer questions, to notice what we are doing and offer genuinely helpful advice – and it will more than likely fail.
Brain-like computers will be able to do all these things and much, much more.