Bottleneck just means that component is holding back the rest of the system. Say you have a video card that is able to achieve 100 FPS in a game but your CPU is only able to do 40 FPS... Your system would run at 40 FPS due to the CPU bottleneck.
My budget for Gpu is 7k.......And my total budget on my cpu is 30k..i ve sufficient money only to buy the gpu n not to upgrade anything else for 6 months.....
Man, you're getting the terms wrong... when you say cpu, its the processor, the chip that is inserted on the motherboard slot, and not the whole system unit. so when you say your whole budget was 30k, I think you were referring to your system unit, itself not only the cpu. Regarding your question. derza is actually right with the bottleneck, its just when a part of your system lets say for example, your cpu, is holding back the capabilities of your video card, or vice versa. No actual physical damage or burn will happen. It's just that your not maximizing all your components.
with a 30k (I dont know your currency but if that is php) budget a quick setup in my mindo would be like this,
i3/i5 3570 with k or not(depends if youll overclock)
h77 or z77 motherboard
4-8 gb ram 1600-1866 depends on your budget
7770 / 650 ti
just make sure that your casing has a good airflow.