We use the future tense "be going to" to express plans and intentions, or to make evident predictions about things we can see will happen. The structure is "be + going to + verb (infinitive)", such as "I'm going to travel to Ireland next summer". We use "will" when making predictions, such as saying "Sue will get a good husband". We also use it for spontaneous decisions ("I'll open the windows") or when offering something to someone ("Will you have some coffee?"). The structure is "will + verb (infinitive)".