When you publish your trips or photoblogs then you will earn the credits from 0-100 depending upon quality and content of it also earn by actively work in this forum. After that you can redeem those credits on Travel for Free Page against some trips which are mentioned there. Some of them includes all things and some of them not included flights .
For ex take Goa trip for 500 which is free for you after redemption but your sharing member needs to pay around 9k for that . so total cost will.be 9k for twin sharing ( you can say ).
For Manali no free trip for anyone so both need to pay some amount.
Yes like if you are redeeming Trip for the 300 credits then there will be twin sharing trip only. So after redemption if trip cost is around 10k per person so you will get in 5k and your sharing member will get in less discount say 7500.