Is it for astronomy or terrestrial use? Some telescopes can be used for either, but more realistically, certain features are optimised for one or the other. There's a couple of major differences between telescopes designed for terrestrial and astronomical viewing. The first concerns how they are mounted on their tripod.
Tripod Mount
'Regular' (i.e. terrestrial) telescopes can be swivelled horizontally, or vertically - just like a camera on a tripod. This is called an altazimuth mount, or AZ for short. Generally speaking, an altazimuth refractor would be better for terrestrial use than an equatorial reflector. Altazimuth refers to the way the telescope is mounted, usually on a tripod. It swings up and down, and side to side, like a camera.
Astronomical telescopes generally use what is called an equatorial mount, or EQ, which has the vertical axis tilted over 23.5 degrees so its parallel with the Earth's axis of rotation. This makes it easier to track stars as they move across the sky, and you can find an object of interest by setting its coordinates (RA & Dec) on the axes' scales.
Primary Optics
A refractor has a lens (like a camera does). A refractor is the 'classical' kind with lenses that you look through, aiming towards the target. A reflector has a curved mirror (concave, like a shaving mirror) at the 'bottom' end, which reflects light up the tube to a small 'diagonal' mirror which reflects the image out the side or sometimes, back down the tube through a hole in the mirror, to a viewing lens (or camera). So you look sideways on to the target. Hubble is a reflector (as Lucy and I well know, having met as programmers for it), whose mirror reflects light back down the tube through a hole in the main mirror (yes, the one that they got wrong).
Now mirrors are good because they reflect different colours equally. If you recall the really cheap microscopes and telescopes you might have had as a child, they had coloured fringes around things. The cross-section of a lens is essentially like a prism. They make nice rainbows. You can overcome that to some extent with expensive combinations of lenses - or by using a mirror. Another good thing about reflector telescopes is you can get a bigger mirror than a lens for the same cost. Bigger is better because you can gather more light, especially necessary at night. Less important during the day, for terrestrial use.
A further, minor difference is that images in terrestrial telescopes are 'right way up', in astronomical telescopes they are 'upside down'. However, you can add an 'erector' lens to convert the astronomical image to a terrestrial one.
One more factor to consider, is aperture. This refers to the diameter of the lens or mirror. The larger it is, the more light it will gather - this is especially important for astronomy so that you can see dimmer or more distant objects. Be advised that some cheap children's telescopes (e.g. Oxbridge branding, again) declare the diameter of the lens, but inside the telescope there is a disc with a smaller hole in it, so that the effective aperture is substantially less. They do this because cheap plastic lenses give really bad images except in the central portion - which only give bad images.
So, when buying a telescope, be aware of the main intended use. You can use a terrestrial telescope for astronomy, but serious astronomers will do better with at least an EQ mount - it gets tedious trying to track objects on 2 axes at once! So, if you really want one for dual use (e.g. for a child who may or may not get into astronomy), which of those features can you sacrifice or compromise? I think you should consider a refractor with a equatorial mount. This way, the user can look 'in the right direction' rather than sideways, which makes it easier to aim; and the equatorial mount makes it easier to track celestial objects, and to find them when you learn about celestial co-ordinates.
For an excellent telescope for astronomy, I recommend the SkyHawk-1145P 114mm (4.5") f/500 Parabolic Newtonian Reflector Telescope.
6 Things To Know About How To Buy a Telescope at About.com Which Telescope is Best for Me? at Starizona.com
