what is meant by left most derivation?

what is meant by left most derivation?

References

Reference NO 1

http://en.wikipedia.org/wiki/Context-free_grammar

Reference NO 2

http://stackoverflow.com/questions/15194103/what-is-meant-by-left-most-derivation

Reference NO 3

http://www.seas.upenn.edu/~cit596/notes/dave/cfg8.html

Reference NO 4

http://www.cs.colorado.edu/~bec/courses/csci4555-f11/meetings/meeting06-markednotes.pdf

Reference NO 5

http://planetmath.org/leftmostderivation

Reference NO 6

http://www.cs.nuim.ie/~jpower/Courses/Previous/parsing/node25.html

Reference NO 7

http://www.cs.sunysb.edu/~cse304/Fall08/Lectures/lrparser-handout.pdf

Reference NO 8

http://link.springer.com/article/10.1007%2FBF01768484