$\mathrm{X}$ and $\mathrm{Y}$

are

Both $\mathrm{X}$ and $\mathrm{Y}$ are conformers of each other, where $\mathrm{X}$ is eclipsed and $\mathrm{Y}$ is staggered form.

Conformers are the spatial arrangements of atoms, which can be converted into one another by rotation around a$\mathrm{C}-\mathrm{C}$  single bond. The conformation in which the substituents are as closed together as possible is called eclipsed conformation, whereas in staggered form the substituents are far apart as possible.