For the single layer(for example Airport layer) there are many entries in the attribute table.
Can we call single attribute row entry a feature of the Airport Layer?
Can somebody give clear view of layer and feature ?
Yes, a layer is a set of features and each feature correspond to one row in the attribute table.
That being said one feature could be composed of several object (or collection) like in the case of multipoint, multiline or multipolygon. In that case each feature is composed of one or several part but all part are grouped in one feature and have one set of attribute (so one line in the table), you may think of a country composed of several island for exemple.