What exactly does sour cream do to a cake when you're baking it? Is it for flavor? Texture?

I've never used it in a recipe before.
TIA!

Sour cream adds moisture and richness, some tang for flavor and it can make the product a bit more tender as the fat limits gluten development while mixing.

Butter is (in the US) 80 percent fat, where sourcream is 20% with a much higher liquid content.

So...could you use butter AND sour cream together?

I use sour cream and butter together in my favorite chocolate cake and white cake recipes. I think it improves everything about the cake.

Every recipe I try with sour cream is awesome. So I am wondering if anyone out there knows how to incorporate sour cream to any cake recipe? Some of my homemade cakes aren't always moist unless there is sour cream in it. I would like to know if there is anyway to just add some sour cream to a recipe that doesn't use it?

I have often just substituted sour cream for the majority of the liquid. Say the recipe calls for 1 cup of milk. I'll add 3/4 cup sour cream and 1/4 cup milk. The uncooked cake will be much thicker but it does work.

And...Mike the cakes I make with sour cream are much more moist than any mix I've ever tasted.