At an opera or play that is being performed in a foreign language, supertitles are a translation or summary of the words, which appear on a screen above the stage.
[US]regional note: in BRIT, use surtitle
supertitle in American English
(ˈsupərˌtaɪtəl)
noun
one or more lines of a translation of the lyrics of an opera, oratorio, etc. in a foreign language, displayed above the stage during a performance