The importance of a graphic card in pc gaming is for rasterizing images while adding light, texture, and color for regular everyday use but, games have to speed this process up to compete with how many frames per second all stored in the RAM and that the GPU can produce. "Since integrated graphics are built into the processor, it typically uses less power and as a result creates less heat, which can result in a longer battery life. A discrete graphics are separate from the processor chip, it consumes more power and generates a significant amount of heat". Discrete graphics cards have better performance because not being connected to a power and memory source it is similar to two persons working together vs; one GPU and processor connected that can't overdo itself or the memory and power are corrupted. 

Source, 1. https://www.studiobinder.com/blog/what-is-motion-blur-definition/. 

2.https://www.intel.com/content/www/us/en/support/articles/000057824/graphics.html.