Ale and lager are the two main beer families. The defining difference is yeast and fermentation temperature, not color or strength. Ales are fermented with ale yeast (Saccharomyces cerevisiae), often called top-fermenting yeast, at warmer temperatures (roughly 60–78°F / 16–26°C). That warmer ferment can create fruity or spicy yeast-derived flavors (esters and phenols).
Lagers use lager yeast (Saccharomyces pastorianus), often called bottom-fermenting yeast, at cooler temperatures (about 48–58°F / 9–14°C). Brewers then typically cold-age the beer (“lagering”) for weeks near freezing, which helps produce a cleaner, crisper profile with fewer yeast-forward notes.
Source: What’s the Difference Between Ale and Lager? — American Homebrewers Association.