CylindricalDecomposition

CylindricalDecomposition[expr,{x1,x2,…}] finds a decomposition of the region represented by the statement expr into cylindrical parts whose directions correspond to the successive xi. 

CylindricalDecomposition[expr,{x1,x2,…},op] finds a decomposition of the result of applying the topological operation op to the region represented by the statement expr.

CylindricalDecomposition[expr,{x1,x2,…},"Function"] represents the result as CylindricalDecompositionFunction[…][x1,x2,…] that can be efficiently used in further computation.

Please visit the official Wolfram Language Reference for more details and examples on core symbols.