Can anyone explain Intel Core "i" numbers?

[x-shaney-x]

I'm buying a new laptop this week and looking around at the various processors listed, I am very confused over what to get.
I have a 1st gen Core i5 (which is much slower than the missus' 1st gen Core i3!) and I am probably going to go for something with a 3rd gen i5.

I understand the difference in generations, just not the actual numbers following as they seem completely random.

For example, an i5-3210M gets pretty decent benchmark scores on passmark but an i5-3427U has a higher number but lower clock speed and lower benchmark.
I have seen quite a few with i5-3315U, which I cannot find any information about anywhere.

I'm not after anything drastically better than the one I have, just something to replace it since the battery is dead and it does not play nicely with linux.

Is there a secret code to all this and does any of it make much difference in the real world?

[forrestcupp]

Your best bet is to check out Intel's web page (http://www.intel.com/content/www/us/en/processor-comparison/compare-intel-processors.html) for processor comparisons. It's a great page for finding out the specific differences in all their processors. As far as I know, the only difference between the i3 and i5 is that the i5 includes the Speed Boost technology, which basically means that when your work needs the extra power, it boosts the speed a small amount.

[ssam]

or https://en.wikipedia.org/wiki/List_of_Intel_Core_i5_microprocessors

[x-shaney-x]

Thankyou both for very useful answers.
I did check intel site but didn't seem to find anything but WTF Wikipedia!!??
A site I use almost on a daily basis and I never even thought to look lol