What are kill line and choke line in drilling?

Kill line is the pumping outlet connected to Mud cross/drilling spool below BOP stack, allow to pump fluid thru it to the annulus while killing/filling operations. 

Choke line is a line connected to mud cross/ driiling spool below BOPs stack, lined up to choke manifold. Its allow to divert the return from the well to the mud system/poor boy/flare pit while killing opeartion and astablish choking pressure on the well if required.  

Kill and Choke lines exit the subsea BOP stack and then run along the outside of the drilling riser to the surface. The volumetric and frictional effects of these long choke and kill lines must be considered to control the well properly.

Kill line is the line connected from kill manifold to NRV. NRV is a non return valve

connected with inner manual gate valve and Gate Valve is coneect to Drilling spool.

the line which connect choke manifold to BOP is known as choke line for keeping back pressure on formation throgh choke while killing well. or it also be used to direct formation fluid away from rig in safe manners.

kill line that line we can use to pump kill mud under pressure.