Visual binary stars can be seen as two separate stars.
Spectroscopic binary stars cannot be viewed as separate stars at any magnification. Their duplicity can only be infered by periodic Doppler shifts of their spectral lines from red to blue and back to red. It is assumed this shift is caused by the orbital motion of the component stars causing them to regularly move toward the earth (blue shift) and away form the earth (red shift). It is possible that one or both of the stars of a visual binary is also an unresolved spectroscopic system embeded within the visual biany.
Eclipsing binary stars cannot be viewed as saparate stars at any magnification, similar to spectroscopic binary stars. Eclipsing systems reviel themselves as binary stars because the two stars regularly pass in front of one another causing them to dim in brightness as one star blocks the light of its companion. In many cases eclipsing binay stars are also spectroscopic binary. It is possible that one or both of the stars of a visual binary also be an eclipsing binary that is embeded within the visual biany.