When in the field on a mission, if you have survivors or team members with you, you can issue them some simple orders. Individual orders can be given by selecting a team member. Group orders can be given using the Team Order buttons down the right side of the screen.

GUI Button Order Description
Gather Gather Pressing this will bring your team running to your side, which is good when a bad situation is brewing. It will be particularly handy during the final fight if you need everyone to Defend.
Defend Defend This will order team members to stand and defend a particular position until you give them another order.
Flee Flee In a bad, baaad situation, you can order team members to head to the Mission Entry / Extraction point. They will do their best to head for it while you hold a line or deter pursuit or whatever.
Search Search Just as you search, you can order a team member to search their surroundings. Their skill at spotting will then come into play, just like yours.
Take Take If containers are found, survivors will grab what they can. If any containers remain lit–up afterwards, you can assume they have no more room and had to leave something behind. It's up to you then to decide if you want to grab it, or have a look at their stuff and drop something to make room.