Electricity that flows without stopping is called what?

Idon't understand what to put on the left lines i'm confused can anyone ?

What are transitions between a liquid and gas called? identify which way they are transitioning

Great amounts of electromagnetic energy from our sun and other bodies in space travel through space. which is a logical conclusion about these electromagnetic waves? their energy must be very their frequency must be very low these waves can travel without a medium they only travel through a vacuum of space