which sitemap submit to webmastertools (i have few sitmeaps on my website)

happy to find this helpfull forum!

YOAST plugin created 2 sitemap for me :

my questions are simple

1. Why 2 sitemaps ?
2. Which one should i add to webmastertools and why ?
3. what about the sitemap www.websitename.com/sitemap ? where is that located or dont need ?

thank you

Poster :