Photoshop’s Select and Mask tool replaces the Refine Edge dialog of previous versions with new, added features, and better “refinement” but at the cost of increased complexity. Rather than re-invent the wheel, I will direct you to some resources which should get you up to speed with this tool.
Note that I recommend using the selection to make a layer mask to hide the background pixels (non-destructive editing), rather than inverting the selection and deleting the background pixels. With a mask, you can always go back later and tweak the mask. If you delete the pixels, there is no going back.
Adobe Resources
Adobe’s training site has a page that outlines all of the tools in the workspace and includes a video by Adobe educator Julianne Kost that works through an example using the refine edge tool. https://helpx.adobe.com/photoshop/using/select-mask.html.
Another Adobe video here shows how to fine tune a selection with Select and mask. https://helpx.adobe.com/photoshop/how-to/make-precise-selections-in-select-mask.html.
Another from Adobe gives a technique that uses a brush made from hair on another image to paint in hair strands on your current image, where the background is too challenging for the select and mask tool to get good separation between hair and background. https://helpx.adobe.com/photoshop/how-to/select-mask-hair.html
Non-Adobe resources
This page covers a range of selection techniques including select and mask. https://www.photography-raw.com/photoshop-selections-select-mask/
Here is another video that works through an example image using select and mask. https://fstoppers.com/photoshop/how-use-photoshops-select-and-mask-workspace-570263
And here is a text and pictures work-through of select and mask from HowToGeek. https://www.howtogeek.com/289255/how-to-make-more-precise-selections-with-photoshops-select-and-mask/