This idea of **asynchronous** code described above is also sometimes called **"concurrency"**. It is different from **"parallelism"**.

**Concurrency** and **parallelism** both relate to "different things happening more or less at the same time".

But the details between *concurrency* and *parallelism* are quite different.

To see the difference, imagine the following story about burgers:

### Concurrent Burgers

* `media_type` - A `str` giving the media type. E.g. `"text/html"`.

FastAPI (actually Starlette) will automatically include a Content-Length header. It will also include a Content-Type header, based on the media_type and appending a charset for text types.

```Python hl_lines="1  18"
{!../../../docs_src/response_directly/tutorial002.py!}
```

### `HTMLResponse`

          break // End of journal.
        }
      }

      redundantOpCount = lineCount - lruEntries.size

      // If we ended on a truncated line, rebuild the journal before appending to it.
      if (!exhausted()) {
        rebuildJournal()
      } else {
        journalWriter?.closeQuietly()
        journalWriter = newJournalWriter()
      }
    }
  }