Hi Jean, great question!
The big difference is between explore and probe is what you are investigating. People explore places like a city, country, ocean, a mine, or another planet. Tools like medical instruments, cameras, sensors, or robots usually probe things. For example, a doctor would use medical device to probe a patient's tumor.
More simply put: people explore and tools are used to probe. More often than not, you explore a place and you probe an object.
This can be very tricky because it is correct to say: "The scientist used an underwater robot to explore the bottom of the ocean". In this example, a tool that is investigating, however it is the scientist who is exploring.
I would like to stress that my answer is not perfect, but it is useful.