This question was asked in solid/chat, and I took the liberty of reposting it here.
A POD is a personal online data storage, meaning a place on the internet where you can store the data you want to store. In terms of Solid it means creating a WebID on a Solid server (on a hosted solution, i.e. a POD provider, or on your own), which also sets up a space for you. Right now we offer solid.community and inrupt.net as POD providers where you can test the concept.
The cloud is a marketing word for servers you don’t necessarily know exactly where are, but you have a service that guarantees you connection to the files or whatever you want from that service.
(Both of these explanations are very simplified of course, but I think they cover what you need to understand in terms of answering this question.)
So to answer your question: There might not be a big difference between a POD and a cloud from the end-user perspective - i.e. a POD might live in the cloud. But a POD might also live on a very specific server that’s not part of the cloud, e.g. it might reside on a server a friend of you set up, where he allows his friends to store data.
Does that answer your question? =)