Type safety means that the compiler will help check that you don't mix (incompatible) data types.
For instance, when you call memcpy, the function (and compiler) only sees two pointers in memory, and will happily start copying data. This means you can mix incompatible data types like this:
SomeClass a;
AnotherClass b;
memcpy((void*)&a, (void*)&b, sizeof(b));
There are many approaches to gaining type safety. You could use templates and make a wrapper around mempcy(), ensuring that the two pointers point to the same data type, or you could use other ways.
Since you are already using vectors from the STL, you are already using a more or less type safe implementation.
