1.5 V batteries are **DC** (Direct Current) batteries.
They provide a constant voltage in one direction, meaning the flow of electric charge (current) only goes in one way. That's what makes them different from AC (Alternating Current), where the direction of current reverses periodically.
So, when you use a 1.5 V battery in something like a flashlight, it powers the device with a steady, unidirectional current.