The Ingress Protection (IP) rating indicates the effectiveness from foreign bodies (i.e. dust) and water moisture. The first digit indicates the protection from foreign bodies and the second the sealing from water moisture, the higher the number the better the protection:
IP6X - Dust Tight - no particle ingress
IPX7 - Waterproof for 30 minutes, up to 1 meter underwater
IP67 - Dust Tight - no particle ingress AND Waterproof for 30 minutes, up to 1 meter underwater