Intel is the best processor manufacturing company besides AMD. Intel has a wide range of processors, which confuse many buyers. A tech enthusiast would know the differences between Core i3, Core i5, and Core i7. Taking consideration of general computer usage person wonders what exactly are this i3,i5,i7, and so on. Knowing the differences helps you to buy a perfect PC for you or your friends or to anyone else.
CPU power runs entirely as the clock speed. The clock speed of a CPU tells how fast a CPU works but not actually how powerful it is.
A CPU with a 3.0 GHz runs faster than a CPU with 2.5 GHz. Intel named their processors differently by using ‘Core’ naming.
 what matters for performance differences?
The main reason for performance differences is in common; The Core i3 processor chips are made for the budget PCs and low-end laptops. A general computer user who does good browsing and watching videos, the i3 processor works fine. The Core i3 processors have a low Cache size.
The mid-range computers have the i5 processors. PC’s with Core i5 are good for an average user and gaming.
The Core i7 CPUs are made for high-end PCs and laptops. These are used by users who do video editing, heavy gaming, and moviemaking.
Number of cores
If you look closely and carefully the main thing you’ll notice from the Core i5 and i7 processors have four cores, whereas the Core i3 models only have two. The cores will affect the performance of the processors the most.
Having multiple cores makes the computer work faster and does ease multitasking. Having more Cores drastically increases the speed of individual programs that are running.

Which One is Good ....???

A Core i3 is good and perfect for day-to-day use, i5 if you want to do video or photo editing, i7 if you do a lot of video editing in 4K.