What does corei5 and corei7 processor mean?

Question 1

Mainly, its just branding and marketing.

In a very general way (but not a fixed rules based on specification):

i7 are quad-core, i5 are dual
clock speed of i7 are faster than i5
i7 have larger cache
HyperThreading is limited to 2 cores for the i5 (so you virtually have 4 cores). A 4-cores i5 will have no HT. i7 up to 6 core have HT (so you virtually have 12 cores)
You'll find only Intel HD Graphics 3000 and 4000 on i7, no lower GPU model, whereas you can find them on i5 (but you can also have HDG 3000 and 4000 on i5).

Read http://www.pcmag.com/article2/0,2817,2404675,00.asp for more détails (I extract these lines from this page)

Answer

Mainly, its just branding and marketing.

In a very general way (but not a fixed rules based on specification):

i7 are quad-core, i5 are dual
clock speed of i7 are faster than i5
i7 have larger cache
HyperThreading is limited to 2 cores for the i5 (so you virtually have 4 cores). A 4-cores i5 will have no HT. i7 up to 6 core have HT (so you virtually have 12 cores)
You'll find only Intel HD Graphics 3000 and 4000 on i7, no lower GPU model, whereas you can find them on i5 (but you can also have HDG 3000 and 4000 on i5).

Read http://www.pcmag.com/article2/0,2817,2404675,00.asp for more détails (I extract these lines from this page)

Question 2

Your question is very vague. Without additional informations on the model of the processor and on the architecture of your machine it is impossible to guess why the performances are similar.

For a real comparison you should have the processor installed on the same hardware and with the same operating system and software running.

Theoretically a i7 should be more efficient due to major cache size and to the ability to support Hyper-Threading.

I suggest you to use some CPU performance tool to inspect your processors.

Searching on the net i5 vs i7 you can find a lot of articles related to this argument (e.g here or here or here, etc).

Answer