I am having a hard time distinguishing the difference between Poisson and Exponential distributions.

Here is the question I am on.

The time between calls to a plumbing supply business is exponentially distributed with a mean time between calls of 15 minutes

a.

What is the probability that there are no calls within a 30-minute interval?

b.

What is the probability that at least one call arrives within a 10-minute interval?

c.

What is the probability that the first call arrives within 5 and 10 minutes after opening?

I am confused about the part when the question asks, for example, "no calls within a 30 minute interval" or "at least one call in a 10 min interval" thanks for any help.