init.el文件内容为什么要加上 ' 才能生效

emacs版本26.3

(custom-set-variables
 ;; custom-set-variables was added by Custom.
 ;; If you edit it by hand, you could mess it up, so be careful.
 ;; Your init file should contain only one such instance.
 ;; If there is more than one, they won't work right.

 '(global-display-line-numbers-mode t)
 '(tool-bar-mode nil))

如果不加 ’ , 那么() 中第一个token当做函数/命令 处理。而global-display-line-numbers-mode是一个变量名不是一个函数。

https://acl.readthedocs.io/en/latest/zhCN/ch2-cn.html#data

谢谢楼上两位的解答,因为刚刚接触Emacs,所以不是很清楚。看了很多网上的配置文件,好像都没有用单引号?