Straight volume is the amount of a product traded over your defined time frame - also known as 'the spikey bits at the bottom of the chart':
Barc
This is the most common volume display, it can be used in conjunction with chart patterns. There is also Open Interest - mainly a futures term. On-balance Volume, volume accumulation etc...etc......
As with all information, it is a personal thing whether you use it as part of your trading or not - personally I have rarely found it to be of much use except in hind-sight, which puts it in the 'chocolate fire-guard' category.
