Refractors, or refracting telescopes, are telescopes that use lenses as objectives to generate images. The objective lens refracts the incoming light to an eyepiece so the image can be seen.

Larger aperture refracting telescopes are much more expensive, exponentially more expensive,  than similar-sized reflectors.  Therefore refractors are typically slimmer than reflectors.  As the light does not get bounced around a few times inside the telescope tube-like with reflector telescopes, for the same focal length, refractors tubes are usually also longer.

Refractors do generate sharper images with higher contrast which makes them better for solar system object observations.

Cooling

Just like reflector telescopes, refracting telescopes need to be brought outside some time before starting observations in order to adapt their temperature to the outside night temperatures.  Although refractors have closed tubes, as they are usually slimmer, or shorter for lower f/ratios, they typically need less cooling time than a reflector telescope.

On top of that, as they normally do not need to be collimated either, you need a lot less time to start observations with a refractor telescope.

Chromatic Aberration

Lenses refract light with different wavelengths under different angles and hence fail to focus the different colors in exactly the same focal point.  This leads to extra coloring on the edges of bright objects against a dark background.

Besides using different types of glass, the effects of chromatic aberration can be minimized by combining multiple lenses:

• Achromatic refractors use two lenses to reduce the effects of chromatic aberration.  For this reason, they are also called ‘doublets’.
• Apochromatic refractors reduce the effects even more by adding a third lens and therefore sometimes are called ‘triplets’.

The extra lenses do come at a serious extra cost.  Apochromatic refractors can be many times more expensive than their single-lens cousins.