An antenna with no gain radiates equally into all portions of the sphere surrounding it. It is by focusing this response into a cone or disc that gain is achieved. An omni directional antenna radiates into a disc which gets thinner with higher gain. A directional antenna radiates into a cone, which may be circular or eliptical and which gets tighter with increasing gain. You should take care to ensure that the output of your system after taking into account all gains and losses does not exceed the legal maximum for your territory.

Indoor Omni Antenna (Doughnut-shaped response) 5GHz - Rubber Duck