How to put text "inside" the image image size

Hi.

How can I put the title “inside” the image? Like the medium title (I want to know how to do it with the post title and with the image caption), like this <a href=”https://medium.com/business-startup-development-and-more/41bde58c832b
“>https://medium.com/business-startup-development-and-more/41bde58c832b

And how can I make the image auto-resize to the full width (also like the image from the link above).