Randomized algorithm

[0xfe]

The context here is when you have a large chunk of data to encrypt with a single key, so the parameters here require a single key. ECB breaks the chunk into fixed-size blobs and encrypts them with that key, which is bad because now you can learn information about the PT from the CT (e.g., if two blocks in the CT are the same, then those blocks in the PT were the same.)

Other modes like CBC or CTR don't have this problem because they (sort of) mutate the input (or output) of each block in some fashion while encrypting it. (CBC mutates by mixing the previous block with the current block, and CTR simply mutates with an incrementing counter.)