The link and button below use pure browser default styling. No CSS has been applied to them. Notice how different they look.

<a> - Link (navigates somewhere):

View my work

<button> - Button (performs an action):

The browser renders these differently on purpose. Links are underlined colored text with a pointer cursor. Buttons get a raised box with a system font. The visual distinction reflects their different roles: links take you somewhere, buttons do something.