What’s the difference between los and las

Both los and las are definite articles for plural nouns in the Spanish language. The difference is that los is used for plural masculine nouns (plural form of el), while las is used for plural feminine nouns (plural form of la). As a good example, we can take the names of cities Los Angeles and Las Vegas. Los Angeles is actually the plural form of el angel, meaning the angel, while the singular form of Las Vegas is la vega, meaning the meadow.

Another example:

el perro - the dog        los perros - the dogs

la vaca - the cow         las vacas - the cows