there are an awful lot of scopes. just go to an optics shop and ask to try some budget scopes, and they'll show you their selection.
The ED model has extra low dispersion glass elements to reduce CA and loss of light.
CA - chromatic aberration. its where you get purple or pink fringes around the edges of high contrast areas.
CA example
DoF - depth of field. its the sharp area that is in focus. a large DoF is where there is more of the image in focus