<?= Html::submitButton('Login', ['class' => 'btn btn-primary', 'name' => 'login-button']) ?>
I would like to understand
'class' => 'btn btn-primary'. btn is a class which is is present in the css file. but where is btn-primary. Are there any other class combinations like the above available in the basic app.
Could some one point me to the direction of a good tutorial which will explain me the basic app in detail.