The filter doesn't change what you can shoot... it changes your shooting "conditions". For example, a 3-stop ND (ND 0.9 when they "density" values and each ".1" is 1/3 of a stop) is EXACTLY like shooting when the light is 3 stops less (which would be 1/8th as much light.)
It doesn't make daytime shots look like evening... they still look like daytime shots. But if there's less light you can respond by either using a wider aperture or a longer shutter time. Usually it's the longer shutter time that you're after (because you could usually can speed up the shutter to open the aperture.) This means you can slow the shutter enough to show some motion-blur in the images (e.g. traffic moving past, water flowing / fountains, etc.)
I should warn you... you can focus with a 3 stop ND filter. You can even focus with about 5 stops. But at 10 stops it will "appear" to be black when you look through (like the filter isn't really transparent at all.) This means you have to use a technique of putting the camera on the tripod, frame up the scene, focus. THEN... turn off auto-focus and carefully thread on the 10-stop ND filter (without disturbing the camera position or focus) and take the shot. Basically it helps to be in manual mode because you wont be able to trust the camera metering and you certain cannot trust the camera focus.
A "quality" ND filter simply reduces the light equally across all wavelengths of the visible spectrum without favoring any wavelength or creating a color-cast or "tint" to the photo AND it does this equally (no darker/lighter regions in the image.)