Some linux system by default starting with gui or (graphic user interface) also called x,but some with the console login, in bothe cases, asking for the user name and password to login.
Gui is more like windows with a start menu ofcourse with some other menus as well.
Console is a unique and powerfull interface of the linux, using shell for the runing commands and starting programs, there are many shells in linux like bash, sh, zsh and etc, the defualt shell for some linux systems are bash.
To change from the default gui login to console login, open the /etc/inittab file in a text editor and change the runlevel from 5 to 3, to start the x or gui from console type:
startx
As well there are many terminals in linux to run the commands in gui like a console, for exmaple gnome terminal, x terminal and konsole a kde terminal.
Also With keys alt+crtl+f6 can change from gui to console and with alt+crtl+f7 from console to gui, and can open more then one console with alt+ctrl+and f1 upto f6.
Root has full permission to the all linux system, but as user has permissions to execute some linux programs, for the others need to get permissions from the root.
If know the root password and want to change from user to the root, in the linuxlinux terminal type:
su
and enter the root password, to go back to the user type exit.
These are some linux commmon commands, if want to know in more details about linux system and commands read rute.pdf.
To get help about any linux command or program in the termianl type:
man command_name or application_name
Also linux has info for commands, to know about info type:
info info

Windows	Linux command	How to run	Defination
0	apropos	apropos   name_group	list the installed application related to the gruop,for example type: apropos browser will list all installed browsers
0	at	at   job   time	executes commands at a specified time
0	atq	atq	lists the user's pending jobs
0	atrm	atrm   job_number	deletes jobs, identified by their job number
0	&	command   &	puts the program in the background
0	bg	bg	reactivate the suspended program in the background
0	bzip2	bzip2   -dvf   file_bz2	decopress bz2 files
0	cat	cat   /path/to/file	writes the contents of the file to the terminale or to other input
open	cd	cd   /path/to/direcotry	open the directories
cd ..	cd..	cd..	go one level up
0	chgrp	chgrp   -R   group   file_name	change the group of file or directory
0	chmod	chmod    -R   0RGO   file_name	change permissions for the file,first zero is not count, R=owner,G=group,O=others,0=no permission,execute=1,write=2,read=4 for example to give all permissions to all: chmod -R 0777 myfile
0	chown	chown   -R   owner   file_name	chang the owner of file or directory
copy	cp	cp -ivr target  destination	copy from the target to the destination
0	crontab	crontab   -e	to run the processes frequently in the given time
0	ctrl+Z	ctrl+z	interrupt a process runing in the foreground
0	crtl+C	ctrl+C	stop a process runing in the foreground
0	df	df	show partitions of hard disk
0	du	du   file_name	estimate file space usag
0	fg	fg	put the background program to the foreground
0	file	file file_name	showt file types
find	find	find   file   search_directory	find the file in this directory
0	free	free	Display amount of free and used memory in the system
0	fsck	fsck    device name or mount point	check and repair Linux file systems
find	grep	ls   |   grep    file_name	use with ls to find the file
0	groupadd	groupadd   group_name	creating group you must be root
0	groups	groups   user_name	show the group of user
0	gunzip	gunzip   file_.gz	decopress the gzip files
0	head	head  lines or bytes   file_name	show the first part of the file
0	history	history   -n   number	show the last n numbers history of bash
0	ifconfig	ifconfig [interface]	configure your network interface
0	jobs	jobs	list the background programs
0	kill	kill   -9   process_number	end the numbered process
0	ldconfig	ldconfig	configure dynamic linker run time bindings
0	less	ls   |   less	list the files partialy, continue with enter
shortcut	link	link   -s   target_file  link_name	create soft links to the files
find	locate	locate  file_name	list directories contains the file
dir	ls	ls  directory_name	list the files in the directory
new folder	mkdir	mkdir   -p    /path/and/name	will create all the directories in the path
same as format	mkfs	mkfs [ -V ] [ -t fstype ] [ fs-options ] partition or mount point [ blocks ]	format &build a Linux file system
0	mount	mount	The command reports all the mounted devices
0	more	ls | more	same as less
delete	mv	mv   direcotry_name	perminently delete file or direcotry
rename	mv	mv   old_file   new_file	rename the file or direcotry
move	mv	mv   -iv   source_pathe   destination_path	moves the file or direcotry from source to the destination
netsate	netstate	netstate	show network statuss
0	passwd	passwd	changing password for the current user
0	ps	ps   auwx	show runing porcess
0	pwd	pwd	show the current working directory
reboot	reboot	reboot	rebooting the system
0	renice	renice   -n increament   process_number	alter priority of runing process
delete	rm	rm   -rf   file_name	delete files or direcotories
0	sleep	sleep   number   s	delay for the specified time in seconds(s),minutes(m),hours(h)
0	su	su	work as root and the user account,you will be asked for the root password
0	tail	tail   lines or bytes   file_name	show the end part of file
0	tar	tar   -zxrf   file_.tar.gz	decopress files tar.gz
0	tar	tar   -jxvf   file_tar.bz2	decopress tar.bz2 files
0	tar	tar   -xvf   file_tar	decompress tar files
0	top	top	display linux tasks
makefile	touch	touch   /path/to/file_name	create the named file in the path
0	uname	uname   -rm	print system information
0	uptime	uptime	since how long the system is runing
0	useradd	useradd   -g  group_name   user_name	add new user you must be root
0	userdel	userdel   user_name	delete the user you must be root with -r will delete the home directory as well
0	vmstate	vmstate	report virtual memorry statistics
0	w	w	who is logged on and what are doing
0	wall	wall   message	send the message to every bodies terminal who is logged on
find	whereis	whereis   program_name	search a program or file and show the path
0	which	which   program_name	show the path of the program
0	who	who	show who is logged on