Tower’s explanation of blobs is kind of strange and not really correct. In a general sense a binary blob is just a situation where you have open-source software that is combined with proprietary components.

Most relevant example to the meme is that the Linux kernel is open-source, but can sometimes contain drivers that are proprietary and don’t have source code available. Those proprietary drivers would be the blobs.

As a counter-example, the linux-libre kernel that devfuuu linked to, is a version of the Linux kernel that has had all the blobs removed.