'ipfs object stat' is a plumbing command to print DAG
node statistics. <key> is a base58 encoded multihash.
It outputs to stdout:

  NumLinks        int number of links in link table
  BlockSize       int size of the raw, encoded data
  LinksSize       int size of the links segment
  DataSize        int size of the data segment
  CumulativeSize  int cumulative size of object and references