  This paper deals with a detail study of gravitational collapse of dust and
viscous fluids under the assumptions of spherical symmetry. Our main goal is to
closely analyze the horizons which arise during this gravitational phenomenon.
To this end, we examine the formation and evolution of trapped surfaces in
these spacetimes, with special attention to trapped regions and cylinders
foliated by marginally trapped surfaces. The time evolution of trapped
surfaces, collapsing shell as well as the event horizon are identified
analytically as well as numerically. Using different density profiles of
matter, we analyze, how the nature of the marginally trapped surfaces modify as
we change the energy momentum tensor. These studies reveal that depending on
the mass function and the mass profile, it is possible to envisage situations
where dynamical horizons, timelike tubes or isolated horizons may arise.
