location of additional css class such as rect-title

Hello there….

Today morning I applied site template Yosemite Camp Resort. On homepage, section Why Stay With Us > block Advanced Heading, there is class “rect-title” in field Additional css class(es).
Well, I tried very hard to find code of class mentioned – looked at style.css and many other css files but did not find anything… Could You be so kind and tell me where is the content (programm code) of that class?

I am asking because I saw variuos additional classes in other templates and I am simply courious to know… :o)

Best regards to all of you,
wprat