That will bring up a dialog which looks like this. Each of those icons represents a different mission. Right clicking on one of them will bring up a menu with an eye icon. Releasing the right mouse button while this is selected will give you a brief run down of that mission. It will also let you know how much experience and cash compensation you will receive for completing the mission.
Different missions have different goals.
For example one missions require you to find a specific object, some require you to find a person and some require the elimination of an object. The goals will be explained in the mission briefing. You must click on to your Mission Menu in the upper right hand screen. Move the cursor over the mission and hold the right mouse button. This will bring up some icons that resemble the ones below.