what does ref do in vue

<template>
  <div v-for="(item, i) in list" :ref="el => { divs[i] = el }">
    {{ item }}
  </div>
</template>

<script>
import {
  onBeforeUpdate,
  reactive,
  ref,
} from 'vue';

export default {
  setup() {
    const list = reactive([1, 2, 3]);
    const divs = ref([]);

    // Make sure to reset the refs before each update.
    onBeforeUpdate(() => {
      divs.value = [];
    });

    return {
      list,
      divs,
    };
  },
};
</script>