Analog, digital and hybrid computers are classification of computers based on

Computers can be grouped in several different ways depending on which feature is being compared: by size (supercomputer, mainframe, mini, micro), by purpose (general-purpose or special-purpose), or by how they process data. The analog, digital, and hybrid grouping belongs to this last category, because it is based purely on the type of data-handling technique the machine uses.

A digital computer processes data represented as discrete values, essentially the binary digits 0 and 1, and performs calculations by counting. An analog computer instead processes continuously varying physical quantities, such as voltage, temperature, or pressure, and represents data as a continuous signal rather than as separate steps. A hybrid computer combines both techniques, taking in continuous analog signals, converting them for digital processing, and outputting results in either form. Because the distinguishing factor in every case is how the machine handles and represents data (continuous versus discrete versus a mix of both), this classification is described as being based on the type of data-handling technique.

It is easy to confuse this with classification by purpose or functionality, but purpose refers to whether a computer is built for a single dedicated task or general use, and functionality is a vague term that does not specifically describe the analog/digital/hybrid split. Size classification (mainframe, mini, micro) is a completely separate grouping based on physical scale and processing capacity, not on how data is represented internally.