An Internet browser is a computer program to call websites in the internet and to show their contents correctly on the screen of the user. Well known browsers are "Internet Explorer", "Firefox" and "Opera". In most cases a newly set up computer will already contain an Internet browser. Otherwise or in case you want to use another than the already installed browser you can download the browser of your choice from the website of that browser. Usually they are free of charge.
The selection of the "best" browser is a matter of taste. As they all are capable of doing what they were designed for the differences lie in the range of functions and in the user interface.
Additionally you will often detect slight differences in the way the same website is shown by different browsers. In rare cases it might even happen that one browser is unable to show a certain website while another one has no problems doing it.
"They came to see and to be seen as well"