Ask two questions: Is the speaker addressing a gathered audience, or just talking with someone? and Is the setting formal or everyday? Everyday communicating and public speaking, as in a speech, sit at the two ends this test separates.
The main types and what makes each one distinct
Before reading the list, try one quick test: is the speaker addressing a gathered audience or talking with someone, and is the setting formal or everyday? Each type below differs on at least one of those two points, so the test can place almost any example you hear.
Conversation: everyday speaking with someone, not to an audience. Clue: turns swap freely. Example: Sorry I am late, the bus took forever!
Discussion: speaking in a small group to share ideas and reach a view. Clue: several speakers, one topic. Example: I agree with the plan, but the cost worries me.
Presentation: one speaker explaining prepared content to listeners. Clue: planned structure, little interruption. Example: This chart shows how our sales changed last year.
Debate: formal public speaking where a proposition is presented and opposed, usually followed by a vote. Clue: two sides argue one motion. Example: I will argue that homework should be abolished.
Interview: question-and-answer speaking in a formal setting such as a job talk. Clue: one side asks, the other responds. Example: one speaker asks Tell me about a project you are proud of, and the other answers Certainly. Last year I led a website redesign. Both turns, the question from one speaker and the response from the other, are needed for the exchange to count as an interview; the prompt alone does not make one. The interview example also shows the register these settings call for: in formal public speaking such as presentations, interviews and lectures, grammar, vocabulary and tone stay correct and professional, as in Good morning, everyone. Everyday talk between friends is different and allows contractions and slang, so Hey, morning! fits there.