You have a fixed amount to spend on the two parts that decide how fast a gaming PC feels: the processor (CPU) and the graphics card (GPU). Put more into one and you have less for the other. This guide explains what each part does, what a bottleneck is, and how to split the money sensibly.
The CPU is the game's organiser. It runs the game logic: where every character is, what the artificial intelligence decides, how physics behave, and what needs drawing next. It then hands a list of jobs to the graphics card.
The GPU does the drawing. It turns that list into the picture on your screen, pixel by pixel, many times per second. The more pixels and the prettier the settings, the more work it has.
Together they form a production line. Every frame passes through both, and the line can only run as fast as its slowest worker.
A bottleneck is the part that is holding the other back. If your GPU could draw 120 frames per second but your CPU can only prepare 80 per second, you get 80. The GPU waits around. We call that CPU-limited. If it is the other way round, the CPU waits and you are GPU-limited.
The key point for beginners is that resolution only changes the GPU's workload. A 1440p screen has about 78 percent more pixels than a 1080p screen (3.7 million against 2.1 million), so the GPU has far more to draw. The CPU's job per frame barely changes. That is why a strong GPU matters more as you move to a sharper screen, and why a weaker GPU is often the limit at 1440p and above.
Choose a budget for CPU plus GPU, then slide the split. The bars show a made-up frame rate for each resolution, and which part is the limit.
Things to try. Leave the game type on "Big, pretty game", set the GPU share to 30 percent and watch both bars turn into GPU limits at a low number. Raise the share and the 1440p bar grows, until the CPU starts to hold it back. Now switch to "Fast online shooter". These games are lighter to draw, so the same money gives a higher frame rate, and the CPU becomes the limit sooner. Press the button to see where the made-up balance sits.
For most people playing modern games at 1080p or 1440p, start with the graphics card and give it the largest share, then buy a processor that is good enough not to hold it back. A common split is somewhere around half to two thirds of the CPU plus GPU money on the GPU. The more demanding the settings and the sharper the screen, the more that favours the GPU.
There are good reasons to lean the other way. Fast competitive shooters, big strategy and simulation games, and games with huge crowds or many characters lean harder on the CPU. If you play those on a high refresh rate screen, a stronger CPU pays off. Processors with a large extra cache, such as AMD's X3D chips, are known for helping in many games, though they cost more.
Also remember what the GPU brings with it besides speed: graphics memory. A card with too little can struggle in newer games however fast it is, which is another reason to put money there first.
The picks below are examples at three levels, not reviews. A processor first, then two graphics cards, so you can see how the split shifts as the budget grows.