Qubits are quantum binary digits (bits). These are thought to be the basis of Quantum Computing.
Qubits represent the quantum similarity to digital world of bits. In conventional computing bits show two states of either 1 or 0 and represented physically by a tiny spot on a magnetized disk. Single bit is not meaningful to the human mind but a combination of 8 bits make a byte.
8 bit = 1 byte
that represents useful information such as a letter of alphabet, a number or such other character. But in the concept of quantum computing, qubit can represent both states at the same time in two possible quantum states i.e. |0> and |1>, and it is one of the important tasks in quantum computing to detect the information as |0> or |1>. It is one of the most difficult tasks in quantum computing to maintain quantum quantum entanglement without interaction of external environment.
In supercomputers, scientists are trying to embed the more efficient multitasking procedure and these qubits are effective in doing many operations at a time.
Qubits represent such a wonderful amount of power that about 30-40 qubits are sufficient to go beyond the power of conventional fastest computers but this exists, still, in theory.