The IP rating or International Protection Rating or Ingress Protection Rating indicate resistance of the phone to surrounding environmental conditions. It has latter IP followed by two numbers.
First digit indicates Solids Protection
Second Digit indicates Liquids Protection
IP67 indicates protected from total dust ingress and protected from immersion in water between 15 centimeters and 1 meter in depth.
IP68 indicates protection from total dust ingress and protection from immersion more than 1m.