Semantics
Use accessibility semantics to create accessible rich internet applications. This page describes how to apply accessibility semantics to gov.gr components and patterns.
ARIA Authoring Practices Guide is also a great resource for such accessibility patterns.
Links and buttons
It is strongly encouraged to use the <a> tag with an href attribute. These anchors are typically empty and are neither in the natural tab flow or clickable. This avoids confusing the user by introducing link behavior on an item that does not trigger an action.
While links are meant to take the user to new content, the <button> tag is meant to trigger an action, such as submitting a form.
So, generally there is this rule of thumb: we use a link if there is an href or else we use button with link styles if there no href.
Here are some examples of links and buttons: