Excellent to see you here.
Buddhaghosa was a Sri Lankan commentator who collated, compiled and contribute to the Theravada commentarial tradition, approximately 1000 years after the Buddha.
As for introductions to Theravada Buddhism, check out the pinned Introductory Resources thread in the Discovering Theravada forum.
"Having understood name-and-form, which is a product of prolificity,
And which is the root of all malady within and without,
He is released from bondage to the root of all maladies,
That Such-like-one is truly known as 'the one who has understood'." (Snp 3.6)
"Whether I were to preach in brief, Sāriputta, or whether I were to preach in detail, Sāriputta, or whether I were to preach both in brief or in detail, Sāriputta, rare are those who understand." (A I 333, Sāriputtasutta)