What do CE and BCE or AD and BC Mean?

AD and BC hold religious (Christian) connotations, many prefer to use the more modern and neutral CE and BCE to indicate if a year is before or after.

Common Era (CE) is one of the notation systems for the world's most widely used calendar era.

BCE (Before the Common Era or Before the Current Era) is the era before CE.

BCE and CE are alternatives to the Dionysian BC and AD system, respectively.

The Dionysian era distinguishes eras using AD (anno Domini, "[the] year of [the] Lord") and BC ("Before Christ").

The two notation systems are numerically equivalent: "2019 CE" corresponds to "AD 2019". "5,800 BCE" corresponds to "5,800 BC".