anchor href vs angular routerlink

I am trying to use anchor tag with href in my Angular 7 app. When I click on the link the url changes in the browser but the page doesn't get navigated to. It works if I put target="_self" so this works

<a href="/abcd" target="_self">Abcd</a>

but this does not work only the url changes in the browser but nothing happens

<a href="/abcd">Abcd</a>

where as if I use Angular routing and use RouterLink it works.

<a routerLink="/abcd" routerLinkActive="active">Abcd</a>

Can anyone explain the behaviour please.