Vue directives are attributes prefixed with v- that drive the DOM: v-if displays conditionally, v-for repeats an element for each entry of a list (with :key), v-bind (or :) binds an attribute to data, and v-on (or @) listens to an event.
Example
<li v-for="t in taches" :key="t.id" @click="choisir(t)">{{ t.titre }}</li>