ASIC (Application Specific Integrated Circuit) miner, is a mining machine with chips that are specially designed to mine cryptocurrencies, and they are often pre-programmed to carry out mining for a cryptocurrency. ASIC miners are much more straightforward and user-friendly, almost like plug-and-play with significantly higher returns.
On the other hand, GPU (Graphics Processing Unit) mining comprises of several GPUs (often video cards like Nvidia GTX 1080Ti) bundled together to form a mining rig. Though GPU mining rigs are less noisy, they consume more power and are generally less efficient. But they can still be used for something else and are reprogrammable, which is not the case with ASIC miners.