simple explanation for you :
You have signature space on your ID, placed on bottom of your post. So if you make every single post, the signature will appear bottom of it.
The signature feature added when your level is up, currently you are newbie, there are more level like : Jr.member, member, full member, sr.member, Hero member and legendary.
And signature campaign is a paid campaign from 3rd party company (not official from bitcointalk forum) to borrow/rent your signature space to place their advertisement.
You get payment based on your contract with them, usually pay per post (like 0.0013 BTC / post for a month) or fixed payment for particular post, example get paid 0.08 BTC for 30 post in two weeks.
There are some requirements for campaigner, like minimum level, minimum activity, minimum post and etc. And there are so many rules too, you can check every campaign because they are different for every campaign.
You can check current signature campaign here :
https://bitcointalksearch.org/topic/overview-of-bitcointalk-signature-ad-campaigns-last-update-01-jan-23-615953Good Luck
Are you guys Asians? Like Asian Asians. Not Asian Americans...
because grammar is incorrect?
Look just at Mitchell's thread! 
