Will and (be) going to are interchangeably used to give information about the future. However, note that going to is used when talking about future events that have present reality. In other cases, we use will.
- Tina is going to deliver a baby girl.
- My parents are going to get a new car.
- I wonder if my classmates will recognize me. (Not talking about the present.)
- I hope I'll do better in the test than last time. (Not talking about the present.)
Both will and going to can be used to talk about predictions but going to relies more on outside evidence (what the senses tell) while will is preferred when no such obvious outside evidence is present (ie. predictions based on insights - what we know, believe or have calculated.)
- Look at the sky! It's not going to rain.
- That kid is going to be hit by the car! (spoken: gonna be)
- Don't lend her your dress. She will ruin it. (What the speaker thinks or believes.)
- Donna will certainly resign in less than six months. (What the speaker assessed or calculated.)
Remember that will is usually preferred to (be) going to in formal style. Be going to tends not to be repeated in a text referring pervasively to the future. Take a look at this weather forecast:
- Tomorrow is going to be another hot day. No different than last week, the region will be sweating with 100-degree temperatures and higher. August Fourth will be very similar to Wednesday's forecast.