Most Simplified Explanation != is a field expression that returns every event that has a value in the field, where that value does not match the value you specify. Events that do not have a value in the field are not included in the results. For example, if you search for Location!="Calaveras Farms", events that do not have Calaveras Farms as the Location are returned. Events that do not have Location value are not included in the results. On the other hand, NOT is an operator that returns every event except the events that contain the value you specify. This includes events that do not have a value in the field. For example, if you search using:  NOT Location="Calaveras Farms", every event is returned except the events that contain the value “Calaveras Farms”. This includes events that do not have a Location value.   Here’s an example to illustrate the difference between the two methods. Suppose you have the following events: Table   ID Name Color Location 101M3 McIntosh Chestnut Marin Meadows 104F5 Lyra Bay   104M6 Rutherford Dun Placer Pastures 101F2 Rarity   Marin Meadows 102M7 Dash Black Calaveras Farms 102M1 Roan     101F6   Chestnut Marin Meadows 104F4 Pinkie Sorrel Placer Pastures If you search with Location!="Calaveras Farms", every event that has a value in the Location field, where that value does not match Calaveras Farms, is returned. Events that do not have a value in the Location field are not included in the results. The following events are returned: Output Table   ID Name Color Location 101M3 McIntosh Chestnut Marin Meadows 104M6 Rutherford Dun Placer Pastures 101F2 Rarity   Marin Meadows 101F6   Chestnut Marin Meadows 104F4 Pinkie Sorrel Placer Pastures   If you search with NOT Location="Calaveras Farms", every event is returned except the events that contain the value Calaveras Farms. This includes events that do not have a Location value. The following events are returned: Output Table   ID Name Color Location 101M3 McIntosh Chestnut Marin Meadows 104F5 Lyra Bay   104M6 Rutherford Dun Placer Pastures 101F2 Rarity   Marin Meadows 102M1 Roan     101F6   Chestnut Marin Meadows 104F4 Pinkie Sorrel Placer Pastures ... View more