Why using adsense

[jossef]

I have no idea why webmasters using ad sense.
I can understand when you have a directory website to use ad sense. but when you put ad sense in your blog or/and website you are putting a link to your competitors, why is that to send people to your competitors site for 0.05 per click.
Some times webmasters spend up to 5$ per click "on adward or PPC" to lose this visitor for 0.05$ per click.
You can build your own ads to some affiliate products and earn more from these clicks.

[o0DarkEvil0o]

i don't know how earning money from google adsence please tell me what do this? thanks a lot.