GNU GRUB is a Multiboot boot loader. Briefly a boot loader is the first software program that runs when a computer starts. It is responsible for loading and transferring control to the operating system kernel software (such as the Hurd or Linux). The kernel in turn initializes the rest of the operating system

The Grub Boot Loader Manual provides beginners with a simple introduction to the basics and experts will find advanced details they need.

In this you will see the following things below.

1 Introduction to GRUB
2 Naming convention
3 OS-specific notes about grub tools
4 Installation
5 Booting
6 Writing your own configuration file
7 Theme file format
8 Booting GRUB from the network
9 Using GRUB via a serial line
10 Using GRUB with vendor power-on keys
11 GRUB image files
12 Core image size limitation
13 Filesystem syntax and semantics
14 GRUB’s user interface
15 GRUB environment variables
16 The list of available commands
17 Internationalisation
18 Security
19 Platform limitations
20 Outline
21 Supported boot targets
22 Error messages produced by GRUB
23 Invoking grub-install
24 Invoking grub-mkconfig
25 Invoking grub-mkpasswd-pbkdf2
26 Invoking grub-mkrelpath
27 Invoking grub-mkrescue
28 Invoking grub-mount
29 Invoking grub-probe
30 Invoking grub-script-check

You will find all this section offline without any internet connection and learn Grub easily anywhere and anytime.