For a particle moving in space, the quantum state is written as a wavefunction. It plays the same role as the qubit state, but instead of just two amplitudes (for 0 and 1), it has an amplitude for every possible position. You get the probability of finding the particle at a given position by squaring the wavefunction there. Phase still matters -- it determines how the wavefunction interferes with itself over time.

A qubit is like a menu with two items. A wavefunction is the same idea with an enormous menu -- one amplitude for each possible position. The rules are the same (amplitudes combine, then you square to get probabilities), but the menu is much larger.

The wavefunction $\psi$(x,t) is a complex-valued function. Its squared magnitude |$\psi$(x,t)|² gives a probability density for position: the probability of finding the particle between x and x+dx is |$\psi$(x,t)|² dx. Like qubit amplitudes, the wavefunction carries phase information that affects how it evolves and interferes.