What types are and what they do is all well and good, but what I want to know is how they would help me write a larger application. Would it help it be more cor

What types are and what they do is all well and good, but what I want to know is how they would help me write a larger application. Would it help it be more correct, be written faster, or be more flexible? Does it just help on a line-by-line programming basis, or can it have any ramifications on a higher level like product design?