Update 16-Async-EventLoops.md

HariAcidReign · web-flow · commit 90fda4baf060 · 2021-01-14T14:44:16.000+05:30
diff --git a/Notes/16-Async-EventLoops.md b/Notes/16-Async-EventLoops.md
@@ -4,5 +4,20 @@
 
 **Browser has JS Engine which has Call Stack which has Global exec context, local exec context etc**
 - But browser has many other *superpowers* - Local storage space, Timer, place to enter URL, Bluetooth access, Geolocation access and so on
-- Now JS needs some way to connect the callstack with all these superpowers. 
+- Now JS needs some way to connect the callstack with all these superpowers. This is done using **Web APIs**
+
+### WebAPIs
+None of the below are part of Javascript! These are extra superpowers that browser has. Browser gives access to JS callstack to use these powers.
+> setTimeout(), DOM APIs, fetch(), localstorage, console (yes, even console.log is not JS!!), location and so many more..
+
+- setTimeout() : Timer function 
+- DOM APIs : eg.Document.xxxx ; Used to access HTML <html><script><body>..... DOM tree. (Document Object Manipulation)
+- fetch() : Used to make connection with external servers eg. Netflix servers etc.
+
+We get all these inside call stack through *global object* ie. **window**
+- Use window keyword like : window.setTimeout(), window.localstorage, window.console.log() to log something inside console. 
+- As window is global obj, and all the above functions are present in global object, we don't explicity write *window* but it is implied
+
+
+
 
