Basic Back/Lay odds, please explain

[MHunt]

I am new to sportsbetting, so please don't laugh out too loud at my basic question. I am trying to understand back/lay odds as seen on for example betfair.

Lets take a simple example. It is a golf matchup between two players (Bjorn and Fasth). The odds are :

Bjorn ---- Fasth
Back Lay Back Lay
1.75 1.99 2.12 2.4

If I think Bjorn will win, I can "Back Bjorn" and get
1.75 for 1 odds. But why is this not the same as to
"Lay Fasth" (betting that Fasth will NOT win, i.e.
Bjorn will win), which would give me 2.4 for 1, and
thus better odds ? I just don't get it. Please explain.

Thanks,
MHunt

[playersare]

if you lay odds, then the payout is reversed. therefore for Fasth to NOT win, you would have to bet 2.4 to WIN 1.

[balazs]

If you make a Lay bet at 2.4 odds, it means that somebody took a Back bet on the opposite outcome with 2.4 odds.
That somebody bet 1 to win 2.4. He is going to win his 1 investment, plus 1.4 of your money. That 1.4 is your liability. So you're betting that 1.4 to win his 1.0

edit: english grammar is tough.