what does this syntax ( page = $page ? $page : 'default' ) in php mean?

[Exgivrynnqcwg]

i'm new to php. I came across this syntax in wordpress. Can anyone explain to me the last line of that code?\[code\]$page = $_SERVER['REQUEST_URI'];$page = str_replace("/","",$page);$page = str_replace(".php","",$page);**$page = $page ? $page : 'default'** \[/code\]the last line(bolded).thanks