Mindy:

I'm not exactly sure what you're asking, but I'll take a stab at it.  A
combo box on a form can do various things for you, such as allow a user
to select a choice from a list or navigate to a particular record on a
form.

The most common use of a combo box on a form is to allow a user to
select something from a list.  For instance, assume you have a list of
customers who all have a unique ID, but your user has no idea what that
number is.  By building a combo box that looks up the customer ID and
the customer name, your user can type in the customer's name, but the
combo box can store the customer ID for you behind the scenes.  The
'remember the value for later use' just means that the field is unbound
and is not going to fill in a particular field in your underlying data.
Otherwise, choose where you want to store the user's selection in your
data for the form.

By "Navigational", I am assuming you mean a combo box used to navigate
to a particular record on a form.  This type of combo box is useful in
the same manner as described above in that it allows a user to type in
a customer name, but instead of just storing the ID, it takes the user
to that customer's record in your form.  So, if I wanted to go to the
record for ABC Customer, I could just select that from the combo box,
and voila, it would jump me to their record.

Hope that helps,
Jana