Difference between poisson and exponential distribution in the context of request arrivals at server?

I am studying client's request arrival patterns on web and application servers. About web server's request arrival pattern I read that "The request arrival rate on web server follows Poisson distribution". And about application server I read the sentence "The request arrival rate on application server follows exponential distribution. Now kindly explain that is there any difference between Poisson and exponential distribution in the context of client's request arrival pattern on server.