The main point of completing contracts within the game is to be rewarded with money, which you then use to purchase new weapons, gadgets, attachments, and skills. The skill tree is split into four tiers – mask, suit, support, and gadgets.
Whilst most of the contracts will be assassinating targets, there is some variety provided by requiring you to sneak in and download intel or picking up key objects, along with other smaller challenges like taking out two enemies at once, or defeating your target without tripping the alarm that provides further income if successfully completed.
Once you have completed an objective you can proceed to one of the many exfiltration points on the map to upload the intel and be rewarded with your payment. At this point, you can continue on to complete further objectives or leave your current area to go back to the main screen and tinker with your loadout and upgrades or go to a new location.