Apart from the home folder, you need administrator privileges to access the other folders. Although you can look.
= This is the root directory which should contain only the directories needed at the top level of the file structure.  
root folder - home directory for the super user = That's where the root home users directory is if you have a root user account activated on your system. This is different from the / directory, which is the system's root directory.
/bin - essential binary commands = It’s where all the programs live. It contains executable binaries, essential commands to boot the system or in single-user mode, and essential commands required by all systems users, such as cat, cp, ls, mv, ps, and rm. Applications (such as Firefox) are stored in /usr/bin, while important system programs and utilities, such as the bash shell, are located in /bin.
/sbin - binary administration files = Likewise the /bin, the /sbin directory is intended for essential binaries related to system administration, such as fsck, fdisk, ifconfig, shutdown and adduser utilities. To view a list of these programs, type: ls /bin - ls /sbin. On some of the newest Linux distributions /usr/bin and /bin are actually just symbolically linked together, as are /usr/sbin and /sbin.
/boot - boot process files = Contains the files that the kernel needs to boot the machine. The Bootloader lives here and you don't have access. When the system boots up it fires the kernel. The kernel (vmlinuz file with a piece of code) manages the processes, the device drivers and I/O. When it's fired it initializes the hardware and the internal data structures; When it's complete it then starts the init.
/media - removable media = cd drive, dvd drive shows up here or in /run
/dev - device files = On Linux, everything is presented in the form of files. When plugging a USB stick into the computer, for example, a file will be created inside the /dev directory and it will serve as an interface to access or manage the USB drive. In this directory, you will find similar ways to access terminals and any device connected to the computer, such as the mouse. That's also where you can find the /dev/null.
/etc - configuration files = It’s an important folder, it holds all sort of configuration files for the system. You can go in and change a file, because the majority are text files.
/home - personal folders = where the users have their personal folder with their name like /home/renata.
lib & lib64 essential shared libraries = where libraries of the installed packages live, they are like DLLs in Windows. It’s where the libraries used by the commands present in /bin and /sbin are located. The /bin & /sbin executable binaries need these libraries to run.  
/opt - optional packages = Contains sub-directories for optional software packages. It is commonly used by proprietary software, which does not conform to the standard file system hierarchy - for example, a proprietary program can place its files in /opt/application when you install it. Example of it google chrome and teamviewer.
/tmp - temporary files = Where applications and programs store files temporarily. Usually, that directory is cleared out when you reboot your system.
/var - variable data files = That's where a lot of logs and temporary files for the system are stored, these are variable data. This is variable, it changes of size every time the system is running. A good example is the system logs, that is, text-based records of activities performed on Linux, such as logins made over the months.
/usr - user system resources = This directory represents the second largest section of the Linux file structure. A large directory hierarchy that looks a little bit like the root. Many of the directory names in /usr are the same as in root and hold the same type of files. Icons for your desktop are stored here, things the desktop uses. A sufficient reason to justify its size is sharing, as /usr contains read-only files, libraries and binaries used by all users of the system, directly or indirectly.   
/mnt – mount of temporary programs = Used to mount other temporary external file systems, such as cdrom and floppy for the CD-ROM drive and floppy diskette drive, respectively.
/proc – process information = It's a virtual file system created on the fly when system boots and is dissolved at time of system shut down. This directory contains files that reveal information about the resources and processes running on the system. Example: To find out how long your Linux has been in use since the last time it was started, just read the /proc/uptime file with the command 'uptime'.
/srv – service data = Contains data for services provided by the system. If you use the Apache server on a website, you probably store your website's files in a directory within /srv.
/cdrom - historical mount point for CD-ROMs = This directory is not part of the FHS(File System Hierarchy) standard, but you can find it on Ubuntu and other versions of the operating system. It is a temporary location for CD-ROMs inserted into the system. However, the default location for the temporary media is within the /media directory.
/lost+found - recovered files = If the file system fails, a system check will be performed on the next boot. Any corrupted files found will be placed in that directory, so that you can try to recover the data.
/run - temporary application files = It gives applications a standard place to store temporary files, such as sockets and process IDs. These files cannot be stored in / tmp, as files located in / tmp can be deleted.