The phrase "going to" is a common way to express the future tense in English. It is used in two main situations: to talk about plans and intentions (things you already decided to do) and to make predictions based on present evidence. The structure is: subject + am/is/are + going to + base verb. For example: "I am going to visit my grandmother tomorrow." or "Look at those dark clouds—it's going to rain!" The short forms of "going to" are often used in everyday speech to sound more natural, such as: "I'm gonna go," "She's gonna call," or "They're gonna leave." (Note: "gonna" is informal and mostly used in speaking.)

There is a difference between "going to" and "will". Use "going to" when you already decided to do something or when there's present evidence. Use "will" for decisions made at the moment of speaking or for promises and general predictions. For example:

"I'm going to start a new course next week." (planned)

"I think she will love this movie." (a general prediction)

"I'm thirsty." – "I’ll get you some water." (decision made now)

In summary, "going to" shows preparation or evidence, while "will" is more about spontaneous decisions or uncertain predictions.

We have to think in what context they are used.

Will is mostly used when you do not have certain of the action in the future.

"I will be there". (Do we know when? No.)

That's why we use going to.

"I'm going to be there". (Going to is mostly used in the English language to accept that the action is "going to" be done).