1. What is an internal wastegate and how does it work?

From my knowledge, an internal wastegate is built into a turbo that is used for low boost applications and helps vent exhaust gases directly into the exhaust system. Am i right?

2. What exactly is an external wastegate?
3. How does it work?
4. Are there different types (i.e. sizes)?

Here's my understanding.

An external wastegate allows a higher exhaust flow than an internal wastegate, and basically eliminates uncontrolled boost (boost creep). It sits on the exhaust side and can either vent exhaust gases into the atmosphere (which is illegal) or can be plumbed into a downpipe. External wastegates are used for high boost applications.

That brings me to the next question.

5. What is a downpipe?
6. Is it the same as a screamer pipe?


Educated replies are what i'm looking for. Thanks in advance.