Many videos describing quantum computers try to distill and oversimplify everything. Thoughty's takes its time and gives more historical and theoretical context than most.
Because it does take a while to get into the subject, here's a shorter explainer by MIT:
Today's computers use bits—a stream of electrical or optical pulses representing 1s or 0s. Everything from your tweets and e-mails to your iTunes songs and YouTube videos are essentially long strings of these binary digits.
Quantum computers, on the other hand, use qubits, which are typically subatomic particles such as electrons or photons. Generating and managing qubits is a scientific and engineering challenge. Some companies, such as IBM, Google, and Rigetti Computing, use superconducting circuits cooled to temperatures colder than deep space. Others, like IonQ, trap individual atoms in electromagnetic fields on a silicon chip in ultra-high-vacuum chambers. In both cases, the goal is to isolate the qubits in a controlled quantum state.
The processing power possible through these controlled qubits will make today's fastest computers look positively archaic.
Image: YouTube / Thoughty2