In American English soda and pop have the same meaning, but the terms are used in different parts of the country. Lemonade is not generally considered soda in the US because it's not carbonated.

For me, in the UK: "soda" - I only hear this in American English really "pop" - I only hear this from people in the north. I would say "fizzy drink" "lemonade" - It is a type of fizzy drink here, the other common one being "cola" (also called "coke")

We say "soda" in the north and Americans in the south say "pop". I have relatives in West Virginia that say "pop" actually. Hehehehe Lemonade is not soda. It isn't carbonated and is made with lemons. A related drink is Limeade. It is made basically the same but with limes instead of lemons. Here is a photo of lemonade: http://glassfrog.us/wp-content/uploads/2014/10/lemonade.jpg And here is a photo of limeade: http://031b7b3.netsolhost.com/WordPress/wp-content/uploads/2013/07/sparkling-cucumber-basil-limeade.jpg

I the UK (or at least England), "soda" is very uncommon and "lemonade" is the carbonated water with a lemon flavour. There also exists similar things such as limeade, cherryade, appleade, but are not close to being as common. If you were to go to a shop or bar and ask for lemonade you would get what the Americans call soda.

By the way "lemonade" can be carbonated, so the people from the US answering are just saying that their lemonade isn't carbonated.