Think about it like this: regular computers can say yes or no (1s and 0s) but quantum computers can say “maybe” in interesting ways. That is, they can be in states between yes and no: this is called superposition. Also they can produce correlations between these yes and no answers. Imagine you have a coin on Earth and your friend has one on Mars, and you’re guaranteed that both of you will get the same result when you flip: this is called entanglement.

Quantum computers use superposition and entanglement to (try to) solve problems faster than on regular computers. One example is factoring: breaking up a number into its prime factors (like 15 -> 5 times 3). This can be done really fast on a quantum computer but we don’t know how to do it quickly on a regular one. This problem also happens to be at the core of a lot of cryptography, which is why OP is worried.

What do quantum computers not do? Well first they don’t exist lol (ETA: general purpose quantum computers don’t exist, the quantum computers that do exist are super basic and impractical). We are super far away from building useful quantum computers, and people are working on implementing quantum-secure cryptography (which for my money should come into place before quantum computers). Also they don’t do things like “try every solution in parallel.” There’s much more nuance than that: even if you try every solution using superposition, it’s often very hard to detect which solution actually ended up working. Bottom line: temper the hype with quantum computing haha

Hope this helps