Bootstrap was made by twitter

Bootstrap font - different than default chrome

rapid development -
responsive design - works for all 19 standard screen sizes

always 12 columns within a row - grid system

md - minimal screen size
if below md defaults to 100% width

5 sizes: XS, S, M, L, XL
XS <576px -  PHONES
S>576px  - TABLETS
M>768px - LAPTOPS
L >992px - DESKTOPS
XL> 1200px - HDMI TELEVISION

row inside container, columns inside row for this to function

div.row>div.col-md-4*3 - shortcut for div class of row, each with a div & column md 4