A filter can be compared to a single condition in an if-statement. Usually (almost always, see Group) the operators in the if-statement are "&&" (in JavaScript/C#)/"AND" (SQL).
For example, the filters:
reults in the if-statement (pseudo code):
If(asset.asset_type is in the supplied list of asset types AND asset.assetid is in the supplied list of asset IDs AND asset.itemid is in the supplied list of item IDs) {
AddAssetToResults()
}
A filter can be created by selecting the Input tab in the Search Editor and then clicking the "Add" button:
...