We are talking about an intention in the near future with some planning.

Examples:
• I´m going to study tonight.
• She’s going to visit us tomorrow

Una lámpara prendida sobre una mesa

Luguixue (2016). Table lamp [photo]. Retrieved from https://pixabay.com/en/table-lamp-nightlight-learning-1513907/

Talking about the near future with some feeling of certainty.

Examples:
• She looks pale. She’s going to get sick.
• I didn’t study. I’m going to fail my exam.

Mujer rubia enferma

Mojca, J. (2015). Woman blow [photo]. Retrieved from https://pixabay.com/en/woman-blow-blowing-nose-hand-chief-698946/