These three tools are available as an online service and Aladin is also available as a software download:

Simbad is a consolidated astronomy catalogue from a variety of smaller catalogues. It is searchable in a variety of ways; by object name, catalogue number, range of RA-Dec locations and others.

VizieR is an image catalogue that is categorised by wavelength, mission and defining astronomical feature.

Aladin combines Simbad and VizieR to make a sky atlas. Any Simbad search data that the user specifies any way can be overlaid onto any VizieR image to give an in depth and customised atlas of a portion of the sky. The result is similar to viewing on Worldwide Telescope or Stellarium except with much greater flexibility.

All three tools are found at CDS Portal