Gravity is the force that pulls an object of mass to another object of mass. But most commonly known as the force that pulls people towards the center of the earth. Gravity's cause can be explained by Albert Einstein’s theory that said space is a fabric, and this fabric can be bent by objects of mass. The bends created in the fabric are what create gravity. The bigger the mass is, the bigger the bend will be creating a stronger gravitational pull, and the smaller the weaker.
For gravity to occur, the two given masses do not have to be touching, just in the others gravitational field. For example, the earth and moon have gravitational pulls on each other, however they are not touching. The moon is just stuck in earth's dent, or gravitational pull. But the moon doesn't the fall straight down to the earth because of its orbit.
Electromagnetism is the interaction of electric currents and magnetic fields, it can be used to make things like electromagnets by combining the currents/fields. In this case, electromagnetism would be caused by moving electrical currents which create magnetic fields. And connecting a battery to a magnet using thise currents/fields creates an electromagnet. You can make these types of magnets stronger or weaker depending on the battery voltage. A battery with higher voltage makes a magnet stronger, and less weaker.
I can only hope that these aliens can retrieve to their home planet with a new understanding of the forces here on earth, gravity and electromagnetism. The two of which have many similarities but of course a share of differences. Both forces are able to exist and occur without making direct contact between the two necessary objects/elements. However, only gravity is able to exist between everything, while electromagnetism needs certain materials to exist. Go now aliens, and spread news of the great earth forced back on “Eyedoughnt Beleevu”.