Pinned tweets stay at the top of your Twitter profile. Having a pinned tweet means that it is the first thing your followers will see when they click on your profile and the pinned tweet will stay at the top of your profile unless you unpin it.
It is easier to unpin tweets when using the Android App. Locate the tweet on your profile and click on the down arrow. Next, select the option that says “Unpin from profile page”and click "unpin" to confirm.