Voltage is measured in volts, V for short.
Current is measured in amperes, amps for short, or A for shorter still. Actual circuits are usually represented by so-called schematics, where the functionality of each circuit element is represented, rather than its appearance. The lines of different length in the battery schematic represent the stacks of dissimilar metals making up early batteries. The circuit must be continuous to have flow, i.e. current. Water flows downhill.