Hooks

Hooking describes a range of techniques for altering behaviour of some software component by intercepting function calls, message or events passed between software components.

• debugging
• extending functionality
• intercepting hardware events (mouse clicks)

Callback

A callback is a piece of executable code passed as an argument to be called back later.

• implemented as subroutines, lambda expressions, function pointers
• synchronous callbacks called in the function code
• deferred callbacks called after the function returns

Webhooks

A method of augmenting or altering the behaviour of a web page using callbacks.

• "user-defined HTTP callbacks"
• often triggered by some event (pushing code to a repo), comment posting...
• upon event, the source site makes an HTTP request to the URI configured for the webhook
  • with github, webhooks allow you to build or set up integrations around events
  • updated external trackers, trigger CI builds, update backup mirror, deploy to production
  • webhook can be installed on an organization or repo
• github has a list of events that can trigger webhooks