Core i3 / Core i5 / Core i7.
Core i9 will be launched in 2018 for desktop CPUs.
There’s also the Power m-Core Core m series for ultra-book laptops and tablets. Performance is roughly around the Core i3 series. It focuses on saving battery life and reducing heat dissipation. (The Pentium series does not refer to older models like the previous Pentium III / Pentium IV / Pentium D, but to Pentiums launched in 2006.)
(There are other CPU series for special use, only the regular series are selected.)
3. Another thing is that every Core i7 is better than Core i5. It would be a mistake to assume that every Core i3 is better than a Pentium. You need to know the CPU performance of the Core i3 / Core i5, as well as the generation and model number. For example, the $ 130 Core i3 8100 released in 2018 is 60% faster than the $ 500 Core i7 880 released in 2010.
4. Intel Core CPUs (i3 / i5 / i7) display the first generation number. For example, i3-8100 is 8th Generation and i3-7100 is 7th Generation. The i3-6100 is the 6th Generation.