Avidyne IFD540 Pilot's Manual page 172

(FAF) is reached, do not descend – the conditions required to fly
the approach have not been met and you must fly the missed
approach procedure.
WAAS approach types in the Nav Mode datablock include:
LNAV (Lateral Navigation)
Provides lateral (horizontal) guidance only, with standard GPS
precision of 0.3 NM full-scale deflection. This is essentially the
same as a non-WAAS GPS approach. It is flown as any other
non-precision approach – observing step down restrictions,
descend to MDA, fly at MDA altitude to the MAP; and execute the
missed approach procedure if appropriate. Since there is no
vertical guidance associated with this type of approach, the IFD
will not transmit any vertical deviation information. The Nav Mode
datablock will display "LNAV" for the approach type.
LNAV + V (Lateral Navigation with Vertical Information)
This mode provides the same lateral navigation as LNAV, but
also typically presents an ILS GS-like presentation on the
external deviation indicator. The GPS draws a 3-D picture of the
approach based on crossing the FAF at the depicted altitude.
Then it follows a glidepath from the published approach, which is
typically a 3 degree angle to the touchdown zone. This type of
approach remains a non-precision approach and does not
consider any step-down limitations. The Nav Mode datablock will
display "LNAV+V" for the approach type.
LNAV/VNAV (Lateral Navigation with Vertical Navigation)
In this mode, the GPS provides lateral navigation, providing more
accurate guidance than regular LNAV but easier to follow
indications than a localizer. The vertical navigation is driven by
GPS signals. LNAV/VNAV approaches are operationally different
from LNAV+V in that the glide path is protected from obstructions
but attention still must be applied to step down fixes. Also, the
minimum altitude presented is a decision altitude/height (DA/DH)
5-16 Navigation