The Apostolic Fathers show a church already organized around bishops, worship, martyrdom, moral discipline, Scripture, and public teaching received from the apostles.
Why this group is different
The Apostolic Fathers are the earliest Christian writers after the New Testament. They are close enough to the apostles that their testimony is often used as a bridge between Scripture and the later Fathers.
They are not systematic theologians in the later academic sense. Their works are letters, exhortations, church orders, visions, and martyrdom accounts.
What to notice first
Clement shows Roman concern for order in another church. Ignatius strongly emphasizes the bishop, Eucharist, and unity. Polycarp anchors Smyrna to John and Irenaeus. The Didache shows early catechesis and worship practice.
Read them as early witnesses, not as a finished medieval or modern theological manual.
The Shepherd (Vis. 2.4.3) instructs Hermas to give a copy of the book to 'Clement', who will send it abroad. The identification with Clement of Rome is plausible but traditional, and the Muratorian Fragment dates Hermas under Pius I (mid-2nd c.) which would post-date Clement.
These guides summarize the site data. For primary-source details, open the linked figure pages and the methodology notes.