-es is a suffix (an ending added to a word) that serves two main purposes:

1. It makes nouns plural when they end in s, x, z, ch, or sh. You write boxes instead of “boxs,” churches instead of “churchs,” and wishes instead of “wishs.” The extra syllable makes these words easier to say out loud. Try saying “boxs” quickly and you'll understand why we need that extra sound. Similarly, words ending in a consonant plus y change the y to i and add -es: penny becomes pennies, baby becomes babies.
2. It changes verbs to their third-person singular present tense form. When you say “I watch” or “we watch,” the verb is just watch. But when you say “he watches” or “she fixes” or “it buzzes,” you add -es to show that one person or thing is doing the action right now. The same consonant-plus-y rule applies here too: carry becomes carries, try becomes tries.

The -es ending follows the same rules whether you're talking about multiple objects or describing what someone does. Both help make English clearer and easier to speak.