What is Lasagna ..... well it is not correct as definition, because the correct name is Lasagne, a recipe of the Emilia Romagna region in Italy.
Technically speaking the Lasagne are ?layers? (is it correct) of thin fresh pasta divided by meat ragout and Besciamella (a quiet thick sausage of butter, milk and flour). This is the classic recipe.
But is possible also to substitute the meat ragout and the besciamella with other components like, for example, an octopussy ragout or besciamella and basil pesto( a cream made with many very little leafs of basil , sheep's milk cheese, some parmigiano cheese, pine kernel, garlic and olive oil and some cooking salt).
Take a look here
Lasagne recipes
or here (maybe is better)
Lasagne recipes
or here Lasagne recipes
or here
Sea Lasagne
or here
Lasagne
Hope it can help
bye

Lasgne is a broad noodle about 2 1/2" wide .It's a bit wide for anything but a baked casserole [baked lasagne or lasagne al forno ].A meat ragout like bolognese sauce [ragu alla Bolonese] can be made ,very well , with venison or boar and is a good thing for lasagne.Half cook [boil] the noodles and layer with the sauce in a casserole dish and bake and enjoy.

I'm sorry Mete,
but Lasagne in Italy, (Italian recipe dated from 1200/1300) are thin and large squares of fresh pasta often hand made (still today) with the side of 6" or more. They can have the sides large as the casserole sides. Not only meat is used to prepare Lasagne, but cheese and b�chamel sauce too.
But as you can see in the third address, not only the Ragu is used to prepare Lasagne, but pesto, fish and many other variations......enjoy the lasagne variations, you will have tasty surprises.
bye

Stefano, American lasagne is purchased as I described.When you make it yourself you have a choice [they even make that terrible green stuff !!].From what I can find in my books [italian and american] it goes back to ancient roman times .It was originally made just with flour and water, no egg, and baked with cheese.Now of course ,as you say, there is a wide variety .When I make pasta I use my grandmothers matterello to keep it authentic! Enjoy it any way you make it.

Mete, , I surely enjoy them, moreover if they are very "rich and fat".
I have a round form to maintain.