In this simulation, you can look at the difference between a constant temperature (isothermal) process and an adiabatic process. The paths look somewhat similar on the P-V diagram, but you should notice clear differences. Note that an isothermal process has no change in temperature, so the change in internal energy is zero, but in an adiabatic process the heat transferred is zero.

Note that for each press of a button, the volume will change by 1 liter, unless that carries the system off the graph. What are some things that you notice about an isothermal process vs. an adiabatic process?