By fridge/freezer I assume he is talking about a domestic fridge that incorporates a freezer at the top, bottom if drawer style or side by side as opposed to a separate domestic fridge and a separate freezer. most fridge/freezers are all generally "frost free" unless quit old or comparatively small. In nearly all cases the compressor is located at the back at the base of the fridge.
Many of these fridge/freezers incorporate fans to circulate the cold air and most have an aircooled condenser (like small car radiator) located near the compressor to remove the heat absorbed from the cooling coils (evaporators) plus the heat of compression caused by the circulating compressor. The fan draws air through the condenser and discharges it from the bottom of the fridge and therefore needs a space at the back from the wall (approx 75mm) and preferably at least 50mm gap around the top and sides to disipate the hot air and prevent overheating. Overtime lint builds up on the condenser coil and fan blades and reduces the airflow causing overheating. If the gap is sufficient, turn off the fridge check for dust/lint and gently clean the fan and condenserwith a soft brush and then vacuum. Restart the fridge.
NB after turning off fridge wait 20 minutes before restarting to prevent damage to the compressor motor unless you know the fridge has an auto start delay.