Azure Storage Blobs: what kind of blob do I get with GetBlobReference()?

I'm getting a little confused with blobs. I've read some articles that says that there are two kinds of blobs, blocks and pages, but I can see in the SDK's library a third one:

container.GetBlockBlobReference(); // Block Blob, max 64Mb per block,  max 200Gb in total.
container.GetPageBlobReference(); // Page Blob, aligned to 512bytes pages,  max 1Tb in total.
container.GetBlobReference(); // ??

Is CloudBlob a CloudBlockBlob or a CloudPageBlock? Which constrains applies? Do I have to worry about file size and put blocks or pages when I use that reference?

I've been reading MSDN but I cannot find which one is.