What is the use of derived-mode-add-parents?

[Pankaj Jangid <pankaj@codeisgreat.org>]

I am working on a new -ts-mode for Move language. Rust is the closest
language so I am looking at rust-ts-mode's code. There I encountered a
call in the end,

(derived-mode-add-parents 'rust-ts-mode '(rust-mode))

I need help in understanding what this call does. The docstring says this,

--8<---------------cut here---------------start------------->8---
(defun derived-mode-add-parents (mode extra-parents)
  "Add EXTRA-PARENTS to the parents of MODE.
Declares the parents of MODE to be its main parent (as defined
in `define-derived-mode') plus EXTRA-PARENTS, which should be a list
of symbols."
  (put mode 'derived-mode-extra-parents extra-parents)
  (derived-mode--flush mode))
--8<---------------cut here---------------end--------------->8---

Please help me understand, what is the use of parent modes?

At the beginning of the file, there is

--8<---------------cut here---------------start------------->8---
(define-derived-mode rust-ts-mode prog-mode "Rust"
  "Major mode for editing Rust, powered by tree-sitter."
  :group 'rust
  :syntax-table rust-ts-mode--syntax-table
--8<---------------cut here---------------end--------------->8---

What I understand here is that we borrow certain features from parent
modes. But it is not clear to me, how we borrow these features by simply
calling defived-mode-add-parents or define-derived-mode.