added bit about what embedded systems are

website/tutorials/01-embedded-basics.md

@@ -4,7 +4,7 @@ In this tutorial, you'll learn the absolute basics of the embedded world:
 
 ## Contents
 
-- What are embedded systems?
+- [What are embedded systems?](#what-are-embedded-systems)
 - Electronics 101
   - Current, voltage, power and all 
   - Diodes, Resistors, Capacitors
@@ -17,4 +17,25 @@ In this tutorial, you'll learn the absolute basics of the embedded world:
 - Bus Systems
   - UART
   - SPI
-  - I²C / TWI
+  - I²C / TWI
+
+## What are embedded systems?
+
+Wikipedia does a good job defining embedded systems with this opener:
+
+> An embedded system is a computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electrical system.
+
+So at the end of the day, if you are adding any sort of computation to some object who's main purpose is not being a computer, it's an embedded system.
+
+Some examples of Embedded systems:
+- cars
+- industrial control systems
+- mars rovers
+
+### Real time
+
+An important characteristic that's often required for an embedded system is "real time".
+This is simply the ability for the system to respond to an input within a hard deadline, Eg. automatic breaks for a car.
+A general operating system like Linux is not suitable for these applications because it uses time sharing when scheduling tasks/programs, and unreliably responds to important signals.
+
+