Few things are definitively known about Socrates and his philosophy, but at least we have multiple sources for him since two of his students (Plato and Xenophon) wrote about him and he is also caricatured in one of Aristophanes' comedies. More on this can be read in these threads by u/hillsongshood (with useful contributions by others), as well as this by u/White___Velvet, this by u/Voltimand and this by u/PytheasTheMassaliot