Hi!!. We need need to show at the top of a list of items, the label of the section to which they belong. In the attached image shows the idea.

Thank you very much.

You could use the page title through the menu item to do this.

Thanks for your reply, but how would the code for do it??

You don't have to add any extra code. The page title will show up if you enable it through your category menu item.
Its class is componentheading though and not h1 but you can change that if you want.

within the component k2?. Can you specify where to make the change??

Were you able to show your header up to this point?
To change the class you need to make a small change through the category.php of your template overrides. If you do not use template overrides you will have to create them in order to make the change. Read here on how overrides work getk2.org/documentation/tutorials/174-templating-with-k2-and-the-concepts-of-sub-templates

Then open category.php located in template/your_template/html/com_k2/default/ or if you have a custom sub-template edit that one and locate this block of codeChange the <div class="componentheading"> to <h1>.

Can you tell me, how is the process to show the header up??.
The code is great!!

You have to edit the menu item that points to the category you want the title in.
Then in the Page Display Options you choose to show the Page Heading and if you want the title to be different from the menu item title just enter a new title right below where it says "Page Heading".
When you save the menu item and refresh your page you should be able to see the title.