The character sequence /* introduces a multi-line comment. That comment block is terminated by the next occurrence of the */ character sequence. This means you cannot nest these comments within one another. That is arguably bad coding technique anyway.
Multiple line comments are replaced with a single line terminator during the interpretation phase. When the /* ... */ does not have a line terminator inside, it is simply removed prior to interpretation of the remaining line content.
Everything between the start and end of a multi-line comment is ignored.
ECMA 262 edition 2 - section - 7.3
ECMA 262 edition 3 - section - 7.4