what is difference between Strong Typing and Weak Typing ? which one is preffered ? why?

Strong typing :
                        Strong type is checking the types of variables as soon as possible,usually at compile time.
 Weak Typing :
                        Weak Typing is delaying checking the types of system as late as possible usually to run-time.
which one is preferred :
                       Which is preferred depends on what you want. for scripts &quck stuff you. Usually want weak typing.Because you want to write as much as less code as possible. In big programs, strong typing can reduce errors at compile time.