Magnetically confined fusion plasmas such as those generated in tokamaks and stellarators are characterized by a typical shape.
Tokamaks, in particular, are axisymmetric devices, and therefore one can completely define the shape of the plasma by its cross-section.
Generally, fusion machines using a toroidal layout, like the tokamak and most stellarators, arrange their magnetic fields so the ions and electrons in the plasma travel around the torus at high velocities.
Ions and electrons following these lines found themselves moving to the inside and then outside of the plasma, mixing it and suppressing some of the most obvious instabilities.
By increasing the current in one (or more) shaping coils to a high enough degree, one (or more) 'X-points' can be created.