Edit in JSFiddle

var app = angular.module('app', []);

app.controller('appController', function ($scope) {

});

app.directive('circleTag', function () {
    return {
        restrict: 'E',
        template: '<div class="circle">circle</div>'
    };
});
<section ng-app="app" class="container">
    <section ng-controller="appController">
        <circle-tag></circle-tag>
    </section>
</section>
.circle {
    width: 100px;
    height: 100px;
    border-radius: 50%;
    margin: 30px;
    background: #00a;
    text-align: center;
    color: #fff;
}