Cut Marks: They are also referred as crop marks. They define where the paper sheet will be cut/trimmed to get the actual product size.
Bleeds: The term bleed is used for all objects overlapping the border of the design. It gives cropping some room for error beyond the cut marks.
Safe Margin: This is the border which is given on all four edges to ensure that important content (text and design elements) are not cropped during the cutting process.