The IP (International Protection) rating indicates, with two digits, how well a piece of equipment is protected against the ingress of solids and liquids. On a DC fast charger installed outdoors, that spec stops being just another line item and becomes a matter of safety.
The first digit of IP54 (the 5) indicates dust protection: it doesn't block particles entirely, but limits ingress to an amount that won't interfere with the equipment's operation. The second digit (the 4) indicates protection against water splashing from any direction, which is essential for outdoor installations exposed to rain.
For a parking lot, gas station, or service area, this means the charger can operate safely under normal weather conditions without needing a canopy or extra protection, although in areas with very heavy rainfall or direct exposure to pressurized water, a cover is still advisable.
Beyond the IP rating, it's worth checking the equipment's operating temperature range. A strong water-resistance rating doesn't count for much if the charger stops working reliably in January's frost or August's heat at an outdoor installation.