This is not a question, this is the explanation of the game mechanics for one who wants to avoid risks and to create delivery contract.
If you create a contract:
“Reward” is your payment for a delivery. This is the money you should pay if your delivery contract successfull.
“Collateral” is your insurance. This is the money you should receive if your delivery contract failed. You don’t pay it.
Some person can break the contract and take the cargo. Or someone else can shoot a contractor and loot the cargo in space. Or… whatever. Anyway, if contract failed and this is not your fault, you receive collateral. Unconditionally.
If you accept a contract:
A person who accepted a contract, pays “Collateral” at the moment the button “Accept” is pressed and receives it back when delivery completed. Also, this person receives a “Reward”.
Thus, if you are new in transportation, don’t accept suspicious contracts. For example, if the destination (drop-off) is marked by red <!>, or the path crosses low-sec/null-sec, or the collateral million times more than the reward.