My question is, what is the significance of the 3nm process ? And what will that bring to my work as opposed to the 5nm process ?
Not very much, they're both incredibly advanced manufacturing processes that will have almost no impact on your day-to-day work.
But here is my attempt at an ELI5 explanation.
A chip is made of billions of transistors, where each transistor is a special kind of switch. Like a light switch, there is a point A and a point B such that when the switch is "on", electricity can flow from A to B. When the switch is "off", electricity cannot flow from A to B. Unlike a light switch, changing it from "on" to "off" is different. Instead of a movable contactor, there is special material called semiconductor in between A and B. It works by applying a specific voltage to the semiconductor material between A and B to turn it "on". But this creates heat. And the larger the distance between A and B, the more voltage is needed to turn it "on" and the more heat it makes. Multiply it by billions of transistors, and the amount of heat can be substantial. Conversely, the smaller this distance between A and B is, the less voltage is needed to turn each transistor to "on" and there will be less heat. Thus, smaller transistors use less energy and make less heat.
Very generally, that "nanometer" size of a chip refers to this distance - the size of a transistor. Intel, TSMC, and others all measure it differently and define the bounds of it differently. So the number alone is somewhat vague. But generally, smaller nm process means more power efficiency and less heat to deal with to do the same amount of work.
Last little tidbit: we're just about to reach the physical limits. That semiconductor material is silicon. A single silicon atom is ~0.2nm in size. So right now, assuming 3nm is the size of the transistor, that transistor is only 15 silicon atoms thick. Think about that - counting individual atoms! They've started building "up" now (3D FinFET) to cram more material in a smaller space. But still, we're at the molecular level at this point where pretty soon we just won't be able to go any smaller. Technology will progress, I'm sure there will be other advances to make chips more powerful and more efficient. But it won't be by making transistors smaller and smaller forever because they're already about as small as can be.
