I read that in the north of Italy they would use eggs in their recipes (the recipe to make the pasta itself). Is it an actual tradition or is it just a recent trend? I always thought that the pasta was something simple, made with the heart, durum semolina and water.
Although nowadays both are ubiquitous in Italy (and abroad), dried pasta and fresh egg pasta are traditionally associated with different regions of Italy.
Dried durum-wheat pasta originated in the old Kingdom of the two Sicilies, which encompassed the entire Southern Italy, including the island of Sicily, and had its capital city in Naples. Oldest historical records associate the production and consumption of dried pasta with Sicily, but one of the best renowned home of pastifici (artisanal pasta production places) from time immemorial is the town of Gragnano, in the province of Naples.
Still today, the humble spaghetti with tomatoes and basil is one of the iconic food of Naples.
Fresh egg pasta ("fresh" here is referred to pasta, not to eggs, as in "not essiccated") is linked to the historical region of Emilia, part of the River Po Valley.
It is worth mentioning that from a historical point of view this is the reason why spaghetti alla bolognese, one of the best known Italian dishes abroad, is actually a fake one: "bolognese" means "from the city of Bologna", which is the largest city of Emilia. For this reason it was always supposed, from its very own "design", to go well with tagliatelle, which is a classic fresh pasta format.
It's not recent at all, for example lasagne are documented in ancient times. Also dried pasta as spaghetti is very antique.
(From the Italian Wikipedia article on lasagne).
One is not a variation of the other, they are just different preparations... if you really want to see the history ( rather than tradition) then you should also consider all the wheat derivates as bread, pizza, focaccia, quiches....
There are many kinds of pasta. Some are made from flour and water. Some are made from flour and eggs. Sometimes there is oil in the recipe. Some have other ingredients such as spinach or chilli, for colour and flavour.
Pasta made with egg is somewhat richer tasting, and of course the yolk adds colour.
None of these is more "traditional" than any other. Different towns and regions have different traditions.