Answer:
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
