A (Bid) - Bid is the price at which you can sell. The price shown on the screen is the highest / best bid currently available in the market.
B (Offer) - Offer is the price at which you can buy. The price shown on the screen is the lowest / best bid currently available in the market.
C (Name) - Name of the security.
D (Company code) - This is a unique identifier under which a company is traded on the London Stock Exchange. Codes for companies will normally be made up of three or four letters and are generally derived from the Security Name.
E (Closing price) - The previous trading period’s closing price.
F (Normal market size(NMS)) - A London Stock Exchange defined quantity for what a reasonable sized trade is.
G (Last Trade Price) - Shows the price of the last trade.
H (Mid) - Displays the mid-price of the security. The mid-price is the derived median (halfway point) between the bid and offer price.
I (Change) - The change in price between the last trade and previous closing price.
J (Change %) - The percentage change in price between the last trade and previous closing price.
K (Trade Time) - Displays the time the last trade was executed.
L (Trade High) - Displays the current trading period’s highest price.
M (Trade Low) - Displays the current trading period’s lowest price.
N (Cumulative Volume) - Shows the total number of shares traded in the period.
O (Last trade volume) - Shows the quantity of stock bought or sold in that last trade.
P (Trades) - The total number of trades or "bargains" that have been executed duing the day.
Q (Auction Price) - The uncrossing price from the last auction
R (Auction volume) - The number of shares crossed in the last auction.
Whilst Level 1 data gives a good overview of a security, it does not provide any detail as to what is underlying this, what orders are waiting to be executed or how this might influence the next price move. To get a better insight into what is really happening in the market you will need access to Level 2 data.