Cropping

Does the picture lose any resolution after being cropped?

Marco,
No. Well, yes, maybe. It really depends what your definition of resolution is. It can mean different things depending on who you are. I first started working on images for print media so I thought of resolution as ppi (pixels per inch) which translated to dpi (dots per inch) when the image was printed on an output device such as a printer. That's also how Photoshop defines resolution. Just select Image: Image Size and check the Resolution field near the bottom. In this sense (the correct one), NO resolution is lost after cropping. However, since it's become common to trade images over the internet, where actual resolution is a constant (72 ppi), I've heard people say resolution when they actually mean pixel dimensions, such as, "The resolution of that image is 1024 x 768 (pixels)" If that is how you mean it, then yes, cropping reduces the pixel dimensions of your image.