The Forex markets are open 24-hrs a day during most of the week, allowing forex traders a huge flexibility to enter their trades. And as long as the markets are open the prices will be constantly fluctuating as can be easily seen by looking at the forex charts. And it's thanks to this fluctuations that traders can have profitable trades the whole day.
The charting software interprets the constantly changing prices by dividing this data into various time intervals. For each of these intervals the chart will show you the open and close price, along with the high and low price during the interval. Most software packages will allow you to see this price data by clicking on the spot of the chart where you want to check these values.
One very interesting feature of these forex charts is that they will allow you to choose the time interval under which you will be trading. You may look at charts with time intervals going from ticks, 1 min, 5 min, 10 min, 15 min, 30 min and 1 day.
What of these time intervals you use will depend mostly on the amount of time you want to spend monitoring your trade. For example if you want to monitor the trade for only a few hours you should use the 15 min charts. If you would like to enter a trade that will last for an entire day then you should better use the 30 min charts. And if you want to have a trade that stays open during days you should choose the 1 day charts.
Of course the lengths of the trades can vary, and the time interval you see is only a first approximation indicator of how long your trade will stay open.
One more issue with the length of the intervals is how much you will make, in average, per trade. The longer the interval the most profitable the trade will be compared with a short interval. But on the other hand shorter intervals allow for a greater number of trades that will compound and maybe surpass the profitability of the longer intervals.