Ephemera
Things made to be discarded that survived anyway — tickets, menus, posters, handbills. More broadly, anything of transitory existence; in zoology, a mayfly.
Full definition of Ephemera →:: COMPARE ::
EphemeravsArchive
The short answer
An archive is what someone decided to keep. Ephemera is what nobody decided to keep and which survived by accident — which is exactly why it records what archives leave out.
Side by side
| Aspect | Ephemera | Archive |
|---|---|---|
| Survival | Accidental | Intentional |
| Records | Ordinary life | What mattered |
| Selected by | Nobody | Someone |
| Bias | Random | Deliberate |
What each one means
Archive
The contrast above sets out how Archive differs from Ephemera on the points that actually matter.