'what does " || " mean inside an array of function/strings [duplicate]

i'm reading about a ui framework (quasar) and they have a component (q-input) that have a prop(rules) of type array of function/strings

<q-input
        filled
        type="number"
        v-model="age"
        label="Your age *"
        lazy-rules
        :rules="[
          val => val !== null && val !== '' || 'Please type your age',
          val => val > 0 && val < 100 || 'Please type a real age'
        ]"
      />

what i don't understand is what the purpose of the characters (||) that they use to separate function and strings

vue.jsquasar-framework


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