The triangle pattern is known as a bilateral pattern, which means that after a break-out the trend could either continue or reverse. There are basically 3 types of triangles and they all point to price being in consolidation: symmetrical (price is contained by 2 converging trend lines with a similar slope), ascending (price is contained by a horizontal trend line acting as resistance and an ascending trend line acting as support) and descending (price is contained by a horizontal trend line acting as support and a descending trend line acting as resistance).
The more price approaches the apex (where the trend lines converge), the bigger the chance of a break-out. The triangle pattern has completed when price breaks out of it, in either direction. Conservative traders may look for additional confirmation. The target can be estimated by measuring the height of the back of the triangle and extending it in the direction of the breakout. A common stop level lies just outside the triangle.
