suupose u want to from hwh to mumbai , but tkt is in huge wl , then you bokked a tkt from hwh to mumb , and resv upto raipur, .. and with other train no boked the tkt from raipur to mumbai only reservation , you see on the 2nd tkt , that yr first tkt pnr are also printed on this tkt ,thus u can save reservation charege on 2nd tkt. i share what i know , but if here any wrong information plg forgive me .. thanks