First you need to define the button inside a <form> tag in the website template XML

<form action="/Your_controller_name" method="post">
<button type="submit" class="btn">Call a controller</button>
</form>

- Clicking the button submits the form and calls the controller in python

class (Your ClassName)(http.Controller):

@http.route(['/Your_controller_name'], type='http', auth='public', website=True)
def my_controller_method(self, redirect=None, **post):
# Put your code here,

Yes I have this, but I want another button that DOES NOT submit the form, it performs another action