How to practice theme development

Friends, I am a student and pretty much working on the concepts from 20 days. I have an intermediate knowlegde of Php and very good command over html and css.
I want to develop themes so I downloaded a basic theme from wordpress.org repository so that I can duplicate every single word from it to undertstand the working.

But I am not getting it, can anyone tell me how to practice it..what to do yaar… I am just a beginner infront of you guys…Please Please Please share your expierience so that I can get to know how to do it.

the main thing that is blowing my head is.. _e (translation) sprintf..
How can I remove them..can Anyone tell me up…these are for transating, I know but i dont want to use them…How would I change them so that I get to know the basic code..

Thanks in advance,