Does letting your spaguettie sauce sit for a long long time make it taste better?

Hey so im makeing spaguetti. YES i know i spelt it wrong im here for you to help me so please dont try to teach me how to spell. Anyway, after you make your spaguetti sauce,, will it taste better if you let it simmer for a few hours? My mom always did this she said something about the flavors or something....?