Listbox vs Combobox

[WLMPilot]

For some reason, I am having a hard time grasping the difference between
listbox and combobox. I am new to macros in excel. I am creating an order
entry via excel using userforms. Here is the background of it:

Worksheet(Order) = Sheet that userforms are utilized to input data in order
to create supply request for each ambulance station.

Worksheet (Items)
Column A = Item Number, beginning with A4
Column B = Item description, beginning with B4
Column C-? = Max stock levels for each Ambulance base.
Cells C2-I2 (currently have 7 stations, hence ? in above line) =
Station Number (1-7)

Looks like this:
A B C D E F G H I
1
2 1 2 3 4 5 6 7

3
4 101 Nasal Cannula 5 10 5 5 5 5 5
(list continues down to list all stock items available)


Here are the three different ways I need to create a Listbox or combobox.
NOTE: User will enter only an Item number and Qty.

1) Need to create listbox or combobox that list all item numbers on "Items"
so that the user can ONLY enter a valid item number within the list.
Once this is done, I need to pull the item description and max stock level
for the appropriate station. User previously entered Station# in B1 of
"Order"
sheet.

2) Create a listbox/combobox that pulls the station numbers in so that user
can
only enter a valid station number. Currently C2 - I2. If a new station
is built
the supply officer will add the column for new station in column J along
with the
station number (J2). Code needs to pick up new station number
automatically.
NOTE: this may not be the last column that has data within sheet "Items"

3) In Column S, row 1-20, I have each ambulance number (M1, M2, M3, etc).
Need to pull this into a listbox/combobox) for user to choose which
ambulance
get narcotics if needed.

Thanks for you help!!!
Les