What are Child Themes and why use them WordCamp Nepal 2013

It was a great weekend here in Nepal since I got to meet many like minded people and network with them in the annual WordCamp Nepal 2013. All in all it was a great event and am already looking forward to another year’s event. So this year I had opportunity to give a talk and I choose Child Themes as my topic. The reason I took this as topic of my choice because, I have had issues updating themes for clients for quite long. They make a lot of changes to the theme and once it is updated the change is gone and not many people know that there is a simple way to tackle this issue and it’s called “Child Themes” I have uploaded my slide from the event on slideshare and it is present here. I hope you guys find this interesting and a good read.  Also were you there in the event? How did you feel about this and what was you take on my and everyone else’s talk and How do you rate this year’s event?