The line below the top navigation bar links is known as a “navigation breadcrumb“. It serves 2 purposes:

• It informs you where you are in the forum. In this example, we are in the topic NoFollow that is in the forum Asgaros Forum: General Discussion.
• You can click any of the labels to go to that part of the forum. So, in this example, you can click on  NoFollow (which is meaningless because this is where you are); or, click on Asgaros Forum: General Discussion which will take you to that forum showing a list of topics; or, click on Forum which will bring you to the forum “home”.