Short answers, pulled from the story.
The Epic Cycle refers to a collection of ancient Greek epic poems composed in dactylic hexameter that cover the history of the Trojan War. This group includes works such as the Cypria, the Aethiopis, the Little Iliad, and the Telegony alongside non-Homeric epics.
Most knowledge comes from a broken summary found in the preface to the 10th century Venetus A manuscript of the Iliad. Scholars supplement these gaps using other manuscripts that preserve individual summaries like the Cypria alone and evidence provided by the 9th-century scholar Photius confirms the source derives from Chrestomathy written by Proclus.
The cycle contains five books of the Aethiopis describing Penthesileia and Memnon, two books of the Iliupersis detailing the destruction of Troy, and five books of the Nostoi chronicling the return home of the Greek force. Eugammon's Telegony follows Odysseus' voyage to Thesprotia and his demise at the hands of his illegitimate son Telegonus.
The Epic Cycle was not mentioned as a whole until the 2nd century CE though knowledge of a Trojan cycle appeared by the 4th century BCE. Herodotus knew of the Cypria and Epigoni when he wrote his History in the mid-5th century BCE but rejected Homeric authorship for the former.
Some Neoanalyst scholars operate on the premise that Homeric epics were later than cyclic ones and drew on them extensively while others claim Homeric epics draw on legendary material which later crystallized into the Epic Cycle. Proclus suggests plots of non-Homeric epics look designed to integrate with Homer without overlaps.