What does volume mean? Total buy qty, total sell qty while getting a quote.
Volume is the numbers of shares traded. total buy qty is the numbers of shares put to buy in all the buy orders(of which the best 5 you can see in your terminal).
If a person is buying 200 shares, in turn he will be buying 200 shares from someone. Here the volume 200 is both the buy quantity for buyer and sell quantity for seller. In other words it is the traded quantity, to say in common.
So what you see in the trading terminals, the current market volumes say, 1 min data is the amount of shares traded in a total of 1 minute.