Swap - Lock in LIBOR receiving, background, understand

LorrinCFA

Hey guys,

Could someone with a solid background and understanding of fixed income (specifically swaps) explain to me how through a swap you can lock in a 3 - month LIBOR?

I have read the CFAI text but I would like a more intuitive explanation.

I don't understand (p.235, Reading 55) how the party who pays a floating rate locks in a borrowing rate (if it pays floating how can he lock in???) and how the party receiving a floating payment locks in an amount to be received (since he receives floating payment!!)

Thank you in advance!