Compare and contrast reflection, refraction, and dispersion. Please help, I don't understand, my teacher said I could do it in a table.

To effectively compare and contrast these three things, you need to show how they are all alike and how they are different.  For the "alike" part, they are all properties light waves demonstrate.  The "different" part gets a little more detailed.

Reflection is the return of the light wave from the media it interacted with back to the media it came from.  It does not enter the new media; rather, it is "bounced" off of...

To effectively compare and contrast these three things, you need to show how they are all alike and how they are different.  For the "alike" part, they are all properties light waves demonstrate.  The "different" part gets a little more detailed.

Reflection is the return of the light wave from the media it interacted with back to the media it came from.  It does not enter the new media; rather, it is "bounced" off of it.  This is what happens with most shiny, chromed surfaces.  They reflect the light right back into the air.

Refraction is the bending of light as it interfaces between two different media, each having a different speed for the the light wave involved.  A good example here would be a glass of water half full, with a drinking straw in it.  The straw will appear broken or disjointed, because of the two different speeds of light, in air and water.

Finally, dispersion is what happens when visible light is separated into it's constituent colors by a triangular prism of glass.  A rainbow of colors is produced, each color having it's own wavelength and frequency.  The pattern usually follows the ROYGBIV mnemonic, with red, orange, yellow, green, blue, indigo and blue colors being produced.

As far as a table is concerned, two headings should be listed at the top, one for "alike" and one for "different."  List each characteristic to the left, then fill in the space under the "alike/different" descriptors with the information listed above.