why str=”Hello “+ x?”Man”:”World” and str=”Hello “+ (x?”Man”:”World”) is different?

Can anyone explain why these two strings are generating different outputs….

   var x=true ;
   var str1="Hello "+ x?"Man":"World" ; 
   var str2="Hello "+(x?"Man":"World") ;
   document.write(str1+"<br>"+str2) ;

Str1 prints “Man” and Str2 prints “Hello Man”