How is the Hubble Telescope different from other telescopes orbiting the earth?
The Hubble telescope is designed to look at primarily visible light.
Different types of electromagnetic radiation (light) require different instruments in order to study them. The Hubble space telescope is designed to observe visible light as well as near infrared and ultraviolet light. Hubble's range, however, only constitutes a small portion of the entire electromagnetic spectrum.
For comparison, the Chandra space telescope observes the x-ray part of the spectrum, Spitzer's instrumentation is designed to observe infrared light,
Aside from instrumentation, Hubble is a publicly funded observatory, meaning that anybody can submit a request for time on the telescope. This is not the case for many privately funded space telescope.