Why can we see the moon but we can't see the other planets

We can all see the Moon, Mercury, Venus, Mars, Jupiter, Saturn and even Uranus (if you know where to look)

With a telescope we can see Neptune. ^

So what planets are you referring to that we can't see?

The moon is a lot closer to Earth when compared to any other object, thus it looks much bigger.
Mercury, Venus, Mars, Jupiter, Saturn can be seen with the naked eye from Earth. Uranus, Neptune can only be seen with a telescope.

Distance from Earth (at closest point in its orbit)
Moon = 384,400 km
Venus = 38 million km
Mars = 56 million km
Mercury = 77 million km

Venus, Mars, Mercury are the three closest planets to Earth and as you can see, their distance is much much much greater then that of the moon. That is why the moon appears so large while the other planets appear so small.

As a lot of the above answerers state, several planets in our solar system can be seen with the naked eye, due to the distance to thees planets they appear to the naked eye as stars, most brighter than the surrounding stars. You need to know where to look in the sky, if you have a smart 'phone you could download an app called Google Sky Map, this works of the GPS system within the 'phone and when you point you 'phone at the sky the screen will show you the stars or planets you are looking at and also name them.
If you don't have a smart 'phone here are some helpful links.
http://www.astronomynow.com/sky_chart.shtml
http://astronomycentral.co.uk/planets-to-see-in-the-sky-tonight
http://earthsky.org/tonight
http://www.nakedeyeplanets.com/

Good luck spotting the planets

Venus, Mars, Jupiter and Saturn are all easy to see with the naked eye. Venus and Jupiter are unmistakable. There is no star in the night sky anywhere near as bright as they are. Mercury is also visible to the naked eye but can be a bit tricky to spot. Uranus and Neptune can both be seen through binoculars or a small telescope.