You are correct enough here. The interesting question is not how they are different, but what the advantages are. An FPGA is really good at doing a single task

You are correct enough here. The interesting question is not how they are different, but what the advantages are. An FPGA is really good at doing a single task a ton of times. A microprocessor is good at doing a lot of tasks a ton of times. And an ASIC is just a more permanent and more efficient FPGA. So when would I use an FPGA? Let me describe an example: Stream processing. Let's say I have a stream of data. Like a camera producing a video feed. As each frame of data comes in, we want to compare it to the previous frame and take the average of the two values to create a blurring effect. On a microprocessor we process each frame. We iterate over groups of pixels one at a time, compare it to the value at the pixel in the previous frame and divide by two. Our processing time is a function of the number of pixels we want to look at. If we're lucky we have multiple cores so we can do work in parallel. Maybe even do 32 groups of pixels in parallel on a ryzen or something. But if we have a 1 megapixel image, we're going to still have to visit ~30k pixels sequentially on each core and perform some math. We're probably adding at least a few ms of lag on the feed. And if we're trying to do any multitasking on this cpu, then we may not have very predictable performance. On an FPGA we approach the problem very differently. Instead of having sequential logic for visiting each pixel, we have combinatorial logic. Supposed each pixel came through on a different wire. That wire goes into a component that holds the previous value for the pixel and outputs the average of the current and previous value. We then take that output and rebuild the video feed with it. On a 1 megapixel image, our unit of work is a single pixel and we have concurrency of 1 million units. We add a cycle or two of lag, which is negligible. Additionally, we have very predictable performance because our computation executes in lock step with the system clock. FPGA's are expensive (per unit cost) and aren't always the most efficient. An ASIC will drop per unit cost and power requirements significantly but has a large up front capital investment.