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About 90% of lenses with 'macro' written on them aren't macro at all - they simply focus reasonably close.
Normal lenses are designed so that the subject is far away and the sensor plane is close by. A true macro lens is designed so that they are optimised for the subject close by as well as the film/sensor plane and will give at least 0.5:1 ie 0.5x magnification without any bellows or tubes. In other words, an object 10 mm long will form an image 5 mm long on the film plane or sensor plane.
A true macro lens will be fixed focal length and have opical elements that move in relation to each other as the focas is changed. In comparision, with a normal non-macro or pseudo-macro (close focussing) fixed focal length lens, the lens elements will normally not move in relation to each other, simply in relation to the film/sensor plane. My 50 mm macro has an internal curved rail and slider that moves the individual lens elements in relation to each other as well as their distance from the film plane.
My Olympus 50 mm macro gives 0.5 x with no bellows or tube and 1x with 50 mm of extension. With the bellows, it gives up to about .. 3.4x I think, ie a ladybug will fill the entire 35 mm frame.
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