What is type checking ?

Type checking is feature of the language that deals with whether the language enforces is type rules.
Languages that do require the typing rules as part of its spec's are called strongly type otherwise its weakly typed.

Static typing is when the check is done during compile time, e.g. C, C++, Java e.t.c
Dynamic typing is when the check is done during run time, e.g. Perl, Python, Ruby e.t.c

On major drawback with dynamic typing is that the code would require more testing to capture errors.
Static tying theoretically has a lower execution time, but of course this is not significant in a majority of programs.