Fewest Moves - Insertions?

[philkt731]

I'm quite interested in fewest moves and I can usually get a 36 or 37 or 38 move solve for many scrambles with my best being 30 moves. But For those who can get low 30s a lot, I see they talk about these "insertions" I'm just wondering what they are and what they're used for (maybe an example solve would help...)
Thanks

 

[Marcell]

Example: Guus' solve for FMC #115 at cubestation.co.uk:
Scramble: B2 F' L U R' U F' B U' B2 L2 B2 D2 L2 R B L2 D F' R2 L U2 L D' L2
F2 D' B2 D2 L' B' R' F R . F' D B U2 F U' F' B' U' B U B' U2 leaves 3
unsolves corners.
Then he inserted R B2 R' F2 R B2 R' F2 at the dot, which solves the remaining corners.
That part now looks like R' F R - R B2 R' F2 R B2 R' F2 - F' D B
Which comes out to R' F R2 B2 R' F2 R B2 R' F D B
You can see how moves fall out.

I advise you to take a look at the FMCs at cubestation.co.uk - I'v learned a lot there.