Why Do Some Relays Have Different Maximum Contact Currents And Rated Carry Currents?

Sometimes even if there is sufficient current-carrying capacity between the contacts and conductors connected to the contacts, the contact switching capacity may be small.

Rated Carry Current
The current that can be supplied continuously to contacts without exceeding the maximum temperature when the contacts are not switching.

Maximum Contact Current
The maximum contact current that can be switched. This value must not be exceeded.