If you're putting butter in your coffee to make bullet proof coffee then you want to use grass fed butter.
The grass fed butter comes from cows milk where the cows are fed organically and mostly fed grass to sustain them.
So when you go to the grocery store to buy butter for bullet proof coffee look for grass fed butter or ask an associate where you can find the grass fed butter.
The grass fed butter should be in the same location as the other butter in the store but sometimes in some stores it may be in the organic food section in the fridge.
If you just want butter in your coffee then you can use any type of butter but for bullet proof coffee for weight loss you want to use the grass fed organic butter in the bullet proof coffee.