Isobaric process means constant pressure process.
It is common to have 2 isobaric processes in thermal systems such as vapor compression refrigeration systems, Rankine cycle, gas turbines, etc.
Reason: It is easy to do heat addition or heat rejection at constant pressure.
Most of the above-mentioned systems have phase change processes.
For example in the Rankine cycle boiler converts water into steam and the condenser takes expanded steam at low pressure and temperature and converts it into liquid water.
Similarly, in vapor compression systems the evaporator takes the heat from the surroundings and converts the liquid refrigerant at a very low temperature and pressure into the vapor phase of refrigerant and in the condenser, the high-pressure, high-temperature refrigerant coming out of the compressor throws away the heat to the atmosphere and converts the refrigerant vapor into the liquid phase.
These phase change processes occur at constant pressure and constant temperature.
Hence, most practical thermal systems have 2 isobaric processes.
(It should also be noted that not all practical thermal systems have 2 isobaric processes. For example, the IC engine cycles do not have constant pressure processes where phase change occurs. They are air standard cycles)