All buttons and links should have accessible names. Without a proper label, assistive technologies like screen readers will just announce a button and this gives no information about the button to the listener, for example:
Always add alternative texts in images. If the image fails to load, the alt text is used as a placeholder and the reader will get the info about it.
Always add labels in the form. Labels ensure that form controls are announced properly by assistive technologies like screen readers.
If you wish to dig deeper into accessibility, check out these articles: