You might have gone through the term short circuit while solving electrical circuits. Lets see what is a short circuit in electrical circuits.
When any element between two terminals is replaced by a zero resistance path then it is called as short circuit between two terminals. The voltage across the short circuit is always zero regardless of the current through it. The current flowing through the short circuit path depends upon the circuit condition.
The current flowing through the short circuit path may be zero, positive or negative. The positive or negative current denotes the direction of current flow.
Consider a part of a circuit as shown in figure 1 (i). A circuit element is shown in blue box between two points a and b. A short circuit between points a and b take place by replacing circuit element by a conducting path of zero resistance. This is represented by a red line in the circuit as shown in figure 1 (ii). Now the voltage (v) across points a and b must be zero. But current (I) may have any value depending upon the circuit conditions.
Also Read What is a Open Circuit?