Because this course describes mostly "classic" Wireshark (like almost every Wireshark course),
I use in this course the interface of Wireshark version 1.xx.
Many people still use Wireshark v.1.xx, and I personally really like its interface, but life changes, and many people start using Wireshark 2.x.x or Wireshark 3.x.x which new interface looks a bit different.
However, if you use Wireshark version 2.x.x, you can turn on the classic Wireshark interface by running "Wireshark Legacy" from your system menu
(you will be able to do that if you didn't untick Wireshark 1 when installing Wireshark version 2).
And thus you will be able to do almost everything the same way like I do in this course.
NB! Only Wireshark 2.x.x supports that, but NOT Wireshark 3.x.x.
In Wireshark 3.0.0 and newer versions old GTK+ interface doesn't work anymore.