Formal:
* Elucidate: To make something clear; to explain in detail.
* Expound: To explain or discuss something in detail.
* Articulate: To express clearly and effectively.
* Disclose: To reveal or make known something that was previously secret.
Informal:
* Spill the beans: To reveal a secret.
* Lay it out: To explain something fully and clearly.
* Give the lowdown: To provide all the necessary information.
* Tell the whole story: To recount all the details of an event.
Other:
* Describe: To give a detailed account of something.
* Narrate: To tell a story.
* Relate: To tell a story or describe an event.
* Detail: To give a thorough description of something.
The best term will depend on the specific context. For example, if you are talking about explaining a complex scientific theory, "elucidate" or "expound" might be the best choice. However, if you are talking about telling a friend a gossip, "spill the beans" or "give the lowdown" would be more appropriate.