How Classical Computers Work
Classical computers are the computers we use every day, like laptops and smartphones. They process information using bits, which are the basic units of data. Each bit is either a 0 or a 1, like a light switch that is either off or on. Classical computers perform calculations by manipulating millions or billions of these bits very quickly, but they always process information in a definite state.
How Quantum Computers Work
Quantum computers use quantum bits, or qubits, which work very differently from regular bits. A qubit can be a 0, a 1, or both at the same time through a property called superposition. This means quantum computers can explore many different possibilities simultaneously instead of checking them one at a time. When you measure a qubit, it collapses into either a 0 or 1, but before measurement, it exists in both states at once.
Speed and Problem-Solving
Because quantum computers can process multiple states at once, they can solve certain types of problems much faster than classical computers. For example, they could potentially crack some encryption codes that would take classical computers thousands of years to break. However, quantum computers are not faster at everything. They excel at specific problems like simulating molecular behavior, optimization problems, and certain mathematical calculations.
Key Quantum Properties
Besides superposition, quantum computers use two other important properties. Entanglement allows qubits to be connected so that the state of one qubit depends on the state of another, multiplying the computer's power. Interference is used to amplify correct answers and cancel out wrong ones. These properties together give quantum computers their unique computational abilities.
Current Technology Status
Quantum computers are still in the early stages of development. They are extremely difficult and expensive to build and maintain because qubits are very fragile and sensitive to their environment. Most quantum computers today have only dozens to hundreds of qubits, and they require extremely cold temperatures to operate. Classical computers will likely continue to be used for most everyday tasks for many years to come. 
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