I don't understand how .htaccess works, can you explain?

Question

Apache HTTP Server

The /web folder contains styles, etc. /web/css , /web/js.
This is how everything works, the styles are loaded perfectly

Options +FollowSymLinks
IndexIgnore */*
RewriteEngine on

RewriteCond %{REQUEST_URI} !^/(web)
RewriteRule (.*) /web/$1

Вот так вот стили уже не грузятся на сайте

Options +FollowSymLinks
IndexIgnore */*
RewriteEngine on

RewriteCond %{REQUEST_URI} !^/(web)
RewriteRule (.*) /web/$1

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /web/index.php

If I just remove the slash before /web/ in RewriteCond, then the styles are loaded, why is that? How does it even work

Options +FollowSymLinks
IndexIgnore */*
RewriteEngine on

RewriteCond %{REQUEST_URI} !^/(web)
RewriteRule (.*) web/$1

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /web/index.php