It's kind of like that. The state of a particle in classical mechanics is a linear combination of some basis vectors which are not it's states as such. But th

It's kind of like that. The state of a particle in classical mechanics is a linear combination of some basis vectors which are not it's states as such. But the superposition in QM is the superpositions of states. The phase space in classical mechanics is not a vector space, but in QM it is. This is a fundamental difference because in QM you can take any number of states, make a linear combination a it will result in another perfectly valid state. Not so in classical mechanics. For example, consider a particle orbiting a point. If you take some position vectors as it moves and make a linear combination, the resulting vector will not be a possible position of a particle in this system. In QM, it would necessary be another possible state. This is a slightly sloppy example, but I hope you get the gist.