Backlinks from subdomains are external backlinks or internal backlinks?

Backlinks from subdomains are external backlinks or internal backlinks?

Backlinks from your own site are internal backlinks & help in site ranking in google.

Subdomains SOMETIMES inherit and pass link/trust/quality/ranking metrics between one another
Subfolders ALWAYS inherit and pass link/trust/quality/ranking metrics across the same subdomain

Backlinks are important in seo. Backlinks from subdomain are external links in Seo.

Its External links