This type of formation occurs when there is a resistance level and a slope of higher lows. What happens during this time is that there is a certain level that the buyers cannot seem to exceed. However, they are gradually starting to push the price up as evident by the higher lows.
The buyers are starting to gain strength because they are making higher lows. They keep putting pressure on that resistance level and as a result, a breakout is bound to happen. Now the question is, “Which direction will it go? – Will the buyers be able to break that level or will the resistance be too strong?”
Many charting books will tell you that in most cases, the buyers will win this battle and the price will break out past the resistance. However, it has been my experience that this is not always the case. Sometimes the resistance level is too strong, and there is simply not enough buying power to push it through.