I actually didn't know that. Or should I say, I saw some marketing stuff but didn't understand if an i7 today was any different than an i7 of the same speed from a few years ago. Thanks.
It was Intel's attempt to simplify the marketing for consumers, previously you had Pentium 1-2 etc, core 2 duo etc. and it was a mess of not knowing which is better after a few years. So they simplified it to i3/i5/i7, entry/mid/professional - more recently the i9 which is more or less a Xeon. However they are still generational, and currently on 7th/8th generation (Which is denoted by the first number of the CPU i.e. i7 8XXXU or i5 3XXX). Don't worry about GHz or turbo-boost or any of those numbers, even an entry level i7 is more than enough for most people and the only time you really need to invest research is usually looking at desktop i3's or i5's (Whether they are unlocked and overclockable, how they sustain performance under load). An i7 is always going to be the 'best' (Except that pesky i7 dual core variant, although still technically better), so look at the generation and know the latest one is going to be the better one due to other internal changes. Essentially, GHz is just a single metric on the CPU and if you look over the last 8 years you'll notice it hasn't really changed all that much, however it's more like comparing a 2Ltr car today with one of 8 years ago, there's a lot more than the engine capacity.