Merge

In GIS, merge is a process in which input features from multiple input sources (of the same data type) combined into a single, new, output feature class. The input data sources may be point, line, or polygon feature classes or tables. This operation differs from aggregation in that it maintains the level of dimensionality of the original data (point-to-point, line-to-line, polygon-to-polygon).

Cartographic Generalization
In cartography, merge is one of the operators for Cartographic generalization. As the scale decreases, a number of closely spaced, similar features can be too complex to see clearly, so they can be combined into a single representative feature. Even though the new feature is "false," it generally portrays the existence of the original features.