  We explore the properties of ionized gas in the nuclear and circumnuclear
environment of the narrow-line Seyfert 1 galaxy NGC 4051 using spectroscopic
and imaging observations from the Hubble Space Telescope (HST) and Apache Point
Observatory (APO)'s ARC 3.5m Telescope. We identify an unresolved
moderate-density intermediate width component and a high-density broad
component in the optical emission lines from the active nucleus, as well as
spatially-resolved emission extending up to $\sim$1 kpc in the AGN ionized
narrow-line region (NLR) and $\sim$8 kpc in the stellar ionized host galaxy.
The HST narrow-band image reveals a distinct conical structure in [O III]
emission towards the NE, and the ionized gas kinematics shows up to two
blueshifted velocity components, indicating outflows along the edges of a cone.
We introduce an improved model of biconical outflow, with our line of sight
passing through the wall of the cone, which suggests that the large number of
outflowing UV absorbers seen in NGC 4051 are NLR clouds in absorption. Using
the de-projection factors from the biconical geometry, we measure true outflow
velocities up to 680 km s$^{-1}$ at a distance of $\sim$350 pc, however, we do
not find any rotational signature inside a projected distance $\leq$ 10''
($\sim$800 pc) from the nucleus. We compare the gas kinematics with analytical
models based on a radiation-gravity formalism, which show that most of the
observed NLR outflows are launched within $\sim$0.5 pc of the nucleus and can
travel up to $\sim$1 kpc from this low-luminosity AGN.
