Out-cross just means breeding a line of geckos to a different line to bring in new blood. Basically out-crossing your geckos lower the chances of deformities, etc.
Cross (at least the way I think you’re using it) could just mean crossing a tremper to a super snow.
For instance someone can be line breeding for better CT albinos with the same 1.2 group for a few years then 'outcross' by bringing in a albino from a new source.
Another example, which is technically true out-crossing, is when people take their line and breed it to a completely unrelated source aka wild caught bloodlines.
When you think about the first example, all the albinos are descendant from one animal, so while bringing in a new albino will be broadening YOUR gene pool to some extent, on the macro level you aren't really doing any out-crossing at all.
Wen in-crossing you are pairing related geckos...(son with mother or father with doughters, family related crossings) this is used to create designer morphs and optained any desirered caracteristics that you want on your offsprings!!! ( for example:to create banded or striped animals you have to in-breed your striped female with her best looking striped son... what you are doing is reinforcing (making stronger gens) of this particular carasteristic in future offspring, most likely this will produce more sriped offsprings... or when you have a nice CT on a particular gecko you have to inbreed with one off her offspring that best represent this caracteristic that you are looking foward to achived on your next offsprings (carrot tails) this will produce nice CT... because you are breeding two geckos with a particular gene or caracteristic ...
inbreeding will determine what you will produce....
Wen out-crossing you are pairing geckos that are not related in any way!!!!!
crossing = pairing
english is not my first language and i triyed to explained with the best of my abilities
i hope you understand if not i recommend the herpculture of leopard geckos by: ron tremper. you will find alot of info about in breeding...