Fragment Library vs Mate-pair library

[magicsiew]

The SOLid system allows the research 2 choices for sample preparation, the fragment library or mate-pair library in which fragment library involve single fragment DNA while mate-pair library involve two fragments of DNA.

Why is that need this two different sample preparation method?

What kind of situation we use these different method?

[snetmcom]

mate-pair : structural variation, regions of large repeats or mutations, indels, unique coverage, complex genome snp discovery