  In these notes we give a pedagogical account of the replica trick derivation
of CFT entanglement and its holographic counterpart, i.e. the Lewkowycz
Maldacena derivation of the Ryu-Takayanagi formula. The application to an
'island set-up' for the calculation of black hole radiation entropy is briefly
discussed. Further topics focused on are the relation to thermal entropy,
thermofield double constructions and statements about the emergence of gravity
from entanglement through reinterpretations of gravitational first laws.
