The word "cue" sounds technical, but in behavioural science it simply means any signal, internal or external, that has become associated with an action. A beer advertisement, an internal feeling or a familiar routine such as preparing food may act as a cue, depending on the person and their learned associations.

Consider a missed train (cue). It brings frustration and fatigue (trigger), followed by the thought "I may as well enjoy a drink while I wait" (urge). The drink brings brief relief and next time the link between a disrupted commute and alcohol is a little stronger.