An arraignment is, typically, a defendant's first appearance in court before a judge. A defendant comes to court in one of two ways - under arrest, by the police or under summons, on their own.
At the arraignment the defendant is formally charged with whatever crime(s) he/she is accused of committing. A plea of Not Guilty is entered. Normally, the charges are read in open court by the clerk (the clerk is the person sitting at the desk in front of the judge). For example, if the defendant is accused of Assault and Battery the clerk will say, to the defendant, "[Defendant's name], you are hereby charged with an assault and battery upon [alleged victim's name] on the 11-28-2021. A plea of Not Guilty will enter on your behalf." Of course, the manner in which the charges are read differ from court to court and clerk to clerk, but the principles are the same - inform the defendant of the charge(s), protect the presumption of innocence.
Arraignments are governed under Massachusetts Rule of Criminal Procedure 7.