DNA is data. A blueprint. But new organisms aren't made in a factory, they're made by other organisms, which were made by other organisms, etc. So when environmental factors affect which parts of the blueprint are used in construction of descendant organisms (and we know they can), those organisms can be different even though they share the same blueprint. Think of it as data implicit in code execution state, as children literally fork off the parent process and continue their lives.

Makes sense...what I don't really get is how that means 'heritability' other than through DNA.

Seems to me DNA is kind of like a recipe for beer, and on a humid day the beer comes out a little different with the same recipe. But if you go back to the original weather the beer will come out the same.

So if you sent a Dutch couple of today back in time to the diet and environment of 50 years ago, their kids would be the height Dutchmen would have been 50 years ago, since the DNA and environment are the same. Nothing else changed inside the Dutch that would make their kids taller, and the change in height isn't something that is 'heritable' through other than DNA.

Methylation of cythosines decrease transcription rate. Meaning a gene becomes less active. Methylation state is heritable.

For example, the changes can be other molecules aside from DNA. Like something that attaches to DNA and prevents a gene from being expressed.

What makes such a thing interesting is if it persists through cell divisions, and especially interesting if it is passed down to the next generation. And it turns out that, surprisingly, such things exist.