is it still okay to have windows based app even the features is the same with web based

I know there some experts here. I have a question about windows based and web based. Is it still okay to have a windows based app even the features of the two is the same? I'm asking this because i'm worried about "what if there's no internet?" "How can i use the web based?" And i'm hearing about the intranet. What is intranet?