“Your lunch break is from noon to one.”
You're a manager at a bank. There's a new teller who just started today. You're explaining her work hours. You tell her when she can go to lunch each day.
Your lunch break is from noon to one.
A "lunch break" is some time in the middle of the day when a worker can stop working and eat lunch. For a lot of jobs, the time and length of the lunch break is specific:
Our lunch break starts at 12:30.
I only get a half hour lunch break, and sometimes even that gets cut short!
If someone works in a job with a very flexible schedule, they probably don't talk about their lunch time as a "lunch break". Instead, they might say that they "take lunch" or "have lunch":
I usually take lunch at twelve thirty or noon.
In other words, the phrase "lunch break" sounds like a break which is controlled by the company or by a manager.
In this example, "one" means "1:00 pm". It's common to talk about time just using the number without adding "o'clock":
Let's meet at nine.
"Noon" means 12:00 pm. People usually think of noon as the middle of the day.
12:00 am is called "midnight".