xpma, triggerlines and signal lines are all various type of moving avarages in at least 2 color. for example xpma 34:3 means 34 daily moving avarges with weighted; 34:4 means 34 daily moving avarages with DEMA. ( more explanations can be found if you open the indicator in metaeditor and you may change the default parameters ) in signal line a different type of mathematical weighted moving avarages equation is used. Shortly all are depend on moving avarages but when used in longer time periods ie 34 or more they give good signal about trend and additional idea to gmma.