An isobaric process is one in which pressure remains constant ($\Delta P = 0$) throughout. Isothermal = constant temperature ($\Delta T = 0$); adiabatic = no heat exchange ($Q = 0$); isochoric (isovolumetric) = constant volume ($\Delta V = 0$). In isobaric processes, work done = $P\Delta V$ and both heat and internal energy change.