"Mitverben" can often be translated literally as "verb along". The identity, person and number of co-verbers are unspecified and must be determined pragmatically if required.
The German prefix mit- is productive, i.e. basically you can apply it to every verb. Some forms such as mitgehen, mitkommen, mitfeiern, mitessen, mittrinken, mitreden are used so often that they make it into dictionaries and may even undergo shifts of meaning. Others are made up on the spot on the rare occasions when they make sense:
Willst du die Bleistiftkritzeleien allein entfernen, oder soll ich mitradieren?
For intransitive verbs, "mitverben" typically means that the subject verbs (or the subjects verb) along with someone else. Who that is can be made explicit:
mit jemand mitverben
But conversely, whenever you can say "mit jemand (oder etwas) verben", you can use "mitverben" instead and then optionally drop "mit jemand (oder etwas)". Example:
mit dem Strom mitschwimmen (The stream doesn't actually swim.)
For transitive verbs, these cases where it's not as simple as several people being joint subjects are more frequent because the construction also works with parallel objects. Example:
Der Gesetzesentwurf sieht vor, dass die Fahrkartenkontrolleure in grenzüberschreitenden Zügen die Ausweise der Fahrgäste mitkontrollieren.
This is ambiguous. It could mean either "mit den Grenzbeamten mitkontrollieren" (subject sharing) or "mit den Fahrkarten mitkontrollieren" (object sharing). The same way that in English, the ticket inspectors in cross-border trains may control passengers' ids "along with" either the border officials or passengers' tickets. In English it would be a bit odd to say that they are "controlling the ids along" without specifying who or what they are controlling them along with, but in German that's perfectly idiomatic.