Baking Powder vs Baking Soda - what's the diff?

I've long been confused by Baking Power vs Baking Soda. Yes, I know they are not interchangable, but they look alike, they are named similarly, what's the real difference between them?

Wiki?

Baking powder is a dry chemical used in cooking, mainly baking. Traditional baking powder was composed of a mixture of tartaric acid and bicarbonate of soda (baking soda), a quantity of flour usually being added to reduce the strength [1]. When dissolved in water the acid and bicarbonate react and emit carbon dioxide gas which expands, producing bubbles to leaven the mixture.

Hmmm. Ok Mr. Big words, how about the Soda?

Sodium bicarbonate or sodium hydrogen carbonate is the chemical compound with the formula NaHCO3. Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slight alkaline taste resembling that of washing soda (sodium carbonate). It is a component of the mineral natron and is found dissolved in many mineral springs. The natural mineral form is known as nahcolite. It is also produced artificially.
Since it has long been known and is widely used, the salt has many related names such as baking soda, bread soda, cooking soda, bicarbonate of soda. Colloquially, its name is shortened to sodium bicarb. The word saleratus, from Latin sal æratus meaning "aerated salt", was widely used in the 19th century for both sodium bicarbonate and potassium bicarbonate. The term has now fallen out of common usage.

You lost me at Sodium...

In plain english please?

Baking Soda: Sodium bicarbonate is primarily used in cooking (baking) where it reacts with other components to release carbon dioxide, that helps dough "rise."

Baking Powder: Baking powder is most often found in quick breads like pancakes, waffles, and muffins. Generally, one teaspoon (5ml) of baking powder is used to raise a mixture of one cup (200-250ml) of flour, one cup of liquid, and one egg.

So what's the difference? - Acid!!!

Substituting in recipes

Baking powder is generally just baking soda mixed with an acid, and a number of kitchen acids may be mixed with baking soda to simulate commercial blends of baking powder. The most common suggestion is to use two parts cream of tartar with one part baking soda. Vinegar (dilute ethanoic acid), especially white vinegar, is also a common acidifier in baking. Where a recipe already uses buttermilk or yogurt, baking soda can be used without cream of tartar (or with less). Alternatively, lemon juice can be substituted for some of the liquid in the recipe, to provide the required acidity to activate the baking soda.

Ahhh. Now I get it. Baking Soda + Acid = Baking Powder.

Mystery Solved