Are all sticks of butter "real" butter?

Had an odd thing happen yesterday. Burned a pat if butter in a stainless steel pan. (That part not so odd). As the smoke detector howled I ran the pan outside then back in to open doors & ramp up fans. The weird part was the whole house smelled like burning plastic! I use Costco Organic Unsalted butter which now I suspect is not all butter nor organic. Anyone else have another idea?

The label will state 'BUTTER'....if it doesn't say butter, then it's not butter

You were misinformed. Sounds like you are close to the butter, but not quite there yet. Hopefully you found it.

Imperial Smart Balance, Parkay are all margarine. If it is butter, it will simply say "butter." if the ingredients list either sweet cream or butter and salt, it's butter. If it lists margarine or oleoresins or oil, it's not butter.

Smart Balance, Parkay, etc. are margarine, not real butter. Butter will simply say butter and either be salted or sweet/non-salted.

Read the ingredients. If it has oil in it, it isn't butter. If it is called a butter spread it isn't real butter.