LGA 1150 and 51 refer to microprocessor sockets. A microprocessor socket is what is fitted in a motherboard and defines the compatibility of what processor (CPU) that you can use with your motherboard.
LGA 1150 is also known as Socket H3 and is compatible with Haswell and Broadwell microarchitecture.
LGA 1151 is also known as socket H4 and is compatible with Skylake and Coffee Lake, with the second revision supporting Coffee Lake CPUs exclusively. 
As you might have guessed, the 1151 socket is the more recent/new of the two. If you’re wondering what mobo you actually have, check out our post here to find out.
Differences Between 1150 and 1151
Aside from the fact that the LGA 1151 is more up-to-date tech, it’s actually got an extra pin. What a lot of people don’t know is the number (in the name) refers to the number of pins.
In the past, Intel actually had more pins than either of these numbers but found they could make better microprocessors with 1150 pins. It wasn’t until a few years ago that they found 1151 to be even better for performance, and that’s what is current today.
When Intel upgraded from Skylake to Coffee Lake it was a big improvement, however, they were both using the same amount of pins since they were both built for the 1151 socket. When Intel released Socket H4 the difference was a lot more profound. An extra pin unlocked a lot more power, so it’s kind of like comparing basic broadband with high-speed fiber.
Are 1150 and 51 Compatible?
This is a no. It’s a common question, but they aren’t compatible as the pin difference makes that impossible.
Which Is Better?
Without a doubt LGA 1151 wins every time.
Should I Use LGA 1150?
If you want an honest answer… NO. It’s extremely outdated tech now with limited ability to upgrade. Over the coming years, it will become increasingly harder to find parts. The reality is that LGA 1151 is the here and now. Even the original Skylake microarchitecture is now outdated. So you’ll be living in the dark ages using an 1151.
Should I Use LGA 1151?
YES… But the caveat is you want to make sure you get the correct microarchitecture. You don’t want something massively outdated, but you also want something that your budget will allow. If you want the most recent, check out our best z370 motherboards article which will allow you to use Coffee Lake CPUs. If you’re looking for something a little more in the budget range I recommend Z270 Motherboards which are backwards compatible with Skylake and designed for the more powerful Kaby Lake (Coffee Lake Predecessor).