  Keeping in mind the current picture of an accelerating and flat Universe,
some specific dynamical models of the cosmological term $\Lambda$ have been
selected for investigating the nature of dark energy. Connecting the free
parameters of the models with the cosmic matter and vacuum energy density
parameters, it is shown that the models are equivalent. Using the selected
models, the present values of some of the physical parameters have been
estimated, and a glimpse at the past decelerating universe has also been
presented. It is observed that most of these cosmological parameters nicely
agree with the values suggested by the Type Ia Supernovae and other
experimental data.
