Intel makes 4 lines of laptop cpus. They refer to them as U, Y, H, and one other. Basically, the power draw is the biggest differentiator.
4.5w - MacBook 12" - Fanless
15w - Was used in MacBook Air line
28w - Was used in old 13" pro lines
45w - Quad core, used in 15" lines
The Air is gone now and Apple now uses the 15w cpu in the lower end 2016 13" pros. The 2.0 Skylake gives about the same, probably a little better performance than the old 2.7. Its branding, but the $1499 13" today is really more of a next generation 13" Air. This CPU difference is also why there are only 2 thunderbolt ports vs 4 on the models that use the 28w chip / Touch bar.
Intel causes confusion because the launch of a generation like Kaby lake is spread over a large amount of time. The launch of the first SKU and the date when the whole set of SKUs is available is so long, that it overlaps into the start of the launch of the next generation.
This will only get worse. The Cannonlake line, the first at 10nm will only include the 4.5w and 15w models. We will wait another generation, until Ice lake to see 28w and 45w chips at 10nm. So, intel announced Coffee lake, the 4th iteration of 14nm, which will have the 28w and 45w chips.
Ice lake is probably Q1 2019, so Intel has stumbled badly the past few years. Its all the more amazing to see the gains the ARM designers have been making in comparison.