  The basics of focused transport as applied to solar energetic particles are
reviewed, paying special attention to areas of common misconception. The
micro-physics of charged particles interacting with slab turbulence are
investigated to illustrate the concept of pitch-angle scattering, where after
the distribution function and focused transport equation are introduced as
theoretical tools to describe the transport processes and it is discussed how
observable quantities can be calculated from the distribution function. In
particular, two approximations, the diffusion-advection and the telegraph
equation, are compared in simplified situations to the full solution of the
focused transport equation describing particle motion along a magnetic field
line. It is shown that these approximations are insufficient to capture the
complexity of the physical processes involved. To overcome such limitations, a
finite-difference model, which is open for use by the public, is introduced to
solve the focused transport equation. The use of the model is briefly discussed
and it is shown how the model can be applied to reproduce an observed solar
energetic electron event, providing insights into the acceleration and
transport processes involved. Past work and literature on the application of
these concepts are also reviewed, starting with the most basic models and
building up to more complex models.
