Cruising

so, here's another newbie question.
Maybe there is an article about cruising - what it is, why and how done properly for newbies like my self. why we need it(or don't).
I am gathering info from various youtube chanells I subscribed over the years but would like to hear some of your opinions.
somehow I trust forums a bit more now a days knowing that not all info in youtube is legit.

Thanks for your input!