Question

what is difference between i5 and i7 processor

Answer 1

i5 is either dual core or quad core.
i5 performance is more than sufficient; they will not need the extra performance of the i7 series if their use is limited to web browsing, email, watching video and office/productivity apps. ore i7 processors have an advantage for processor-intensive applications such as video encoding and rendering, 3D modeling, high-end graphics work and gaming. 

Answer 2

For the most part, you'll get faster CPU performance from Core i7 than Core i5. The majority of Core i7 desktop CPUs are quad-coreprocessors, while many mobile Core i5 processors are dual core. This is not always the case, as there are dual-core mobile Core i7 processors and several quad-core desktop Core i5 CPUs.