“We’ll have a question and answer session at the end.”
You're giving a lecture. You say this at the beginning of the lecture so that the audience knows that they should wait until the end if they have questions.
We’ll have a question and answer session at the end.
A "session" is one block of time that you spend with someone for doing a certain task. Examples of "sessions" include:
- a band has a recording session in a studio
- students meet for a study session
- you have a session with a therapist to discuss your emotional problems
A session can be any length, but it's usually between 30 minutes and 2-3 hours.
The words "question" and "answer" often go together. We almost always use them in that order, too: "question and answer".
We also use the phrase "Q & A" as a shortened form of "question and answer":
I read a Q & A with the director of the new Avengers movie that was really interesting.
When events have been planned out at a specific time or in a specific order, you can talk about them with the phrase "We'll have ___":
We'll have breakfast at eight thirty, followed by presentations at nine o'clock.
Use this phrase when talking about work events, conferences, presentations, and so on.