The given relation is
Q=mcΔT
it is a relation between heat given to the system or heat given by the system which brings some change in temperature in the system for a given mass of the system.
"c" represents specific heat : it is the heat released or absorbed by one unit mass of substance when it undergoes ΔT change in temperature
if it is absorbing heat there will be rise in temperature
if it is releasing heat there will be fall in temperature
here
"Q" is the thermal energy
this is the energy given or absorbed by the system.