What are expert advisors for MetaTrader 4?

Beginner Questions
1

Are they an add-on to MT4?
Or template-like things?

2

Altar,

An Expert Advisor in MetaTrader is a program written in MetaTrader’s proprietary software language MQL4 and automates trading activities in the MetaTrader platform. For example an Expert Advisor can create a buy or sell order automatically based on some trading signal that the Expert Advisor is looking out for. You can create custom Expert Advisors using MetaEditor, which is the development plaform for MetaTrader and should be installed on your computer if your using a broker who is using MetaTrader as its trading platform.

Regards,

fishoutawata

3

Thanks, and wow, all automated huh?
I’m saying this because I saw this on youtube: YouTube - Metatrader Expert Advisor and Metatrader Indicators
and I didn’t know what it was.