Limes are a favorite ingredient in many traditional South American recipes, such as the beloved pisco sour cocktail (which just isn't the same when made with ordinary lime juice). South American limes are special - smaller than Persian limes and full of super tart juice. They make the best lemonade (limeade?) you have ever tasted. The closest substitute we have in North America are Florida key limes, which are very similar but not quite as tart.
There's a trick to extracting the most juice you can from these small limes (or any lime, lemon, or orange). Before squeezing the juice from them, heat the limes for a few seconds in the microwave, until they feel warm, then roll them around on the counter, pressing down on them with your palm. The heat makes them limes more flexible and easier to squeeze, and rolling them seems to loosen the fibers inside and free up more juice.
The name for lime in Spanish can be confusing to English speakers. In some Spanish speaking countries, a lime is called a "limón" and a lemon is a "limón dulce" or "limón amarillo"(sweet yellow lime), while in other places lemons are known as "limones" and limes are "limas".