IBM Bluemix使用cf上传代码反馈中的droplet是什么意思？

Question

-----> Downloaded app package (4.0K)
-----> Downloaded app buildpack cache (2.4M)

-----> IBM SDK for Node.js Buildpack v2.6.1-20151015-1326

   Based on Cloud Foundry Node.js Buildpack v1.5.0

-----> Creating runtime environment

   NPM_CONFIG_LOGLEVEL=error
   NPM_CONFIG_PRODUCTION=true
   NODE_MODULES_CACHE=true

-----> Installing binaries

   engines.node (package.json):  unspecified
   engines.npm (package.json):   unspecified (use default)
   Resolving node version (latest stable) via 'node-version-resolver'
   Installing IBM SDK for Node.js (0.12.7) from cache
   Using default npm version: 2.11.3

-----> Restoring cache

   Loading 1 from cacheDirectories (default):

• node_modules
  -----> Checking and configuring service extensions before installing dependencies

-----> Building dependencies

   Pruning any extraneous modules
   Installing node modules (package.json)

-----> Checking and configuring service extensions after installing dependencies
-----> Installing App Management

   WARN: App Management cannot be installed because the start script cannot be found.
   To install App Management utilities, specify your 'node' start script in 'package.json' or 'Procfile'

-----> Caching build

   Clearing previous node cache
   Saving 1 cacheDirectories (default):

• node_modules
  -----> Build succeeded!
  ├── cheerio@0.19.0
  ├── co@4.6.0
  ├── eventproxy@0.3.4
  ├── express@4.13.3
  ├── iconv-lite@0.4.13
  ├── later@1.2.0
  ├── mongoose@4.2.3
  ├── superagent@1.4.0
  ├── superagent-charset@0.0.2
  ├── thunkify@2.1.2
  └── url@0.10.3

-----> Uploading droplet (14M)

---

上面的Uploading droplet是指什么动作？