I’ve often found bibles that have passages with italics in them from time to time. But the italicized words seem so random. I don’t see any pattern to them and I’ve never seen a bible with a page of explanations. What do these things mean?
In most versions italics indicate implied words. If you look you’ll probably notice a whole lot of italicized ‘is’, ‘and’, and other little things like that. They’re not word-for-word present in whatever text they got that translation from, but they’re needed to make the sentences flow, so they’re added in.
What NinjaChick said. IIRC originates as a convention with editions of the “Authorized Version” a.k.a. KJV translation, and picked up by others that tended to imitate that pattern – I can’t help but imagine the translation team was thinking ahead that somebody would whine about a lack of exact word-for-word match and start making accusations about tampering with the original content, so they made visible where thay had to adjust the language to keep it legible.
They’re words required by English syntax for the sentence to make sense, or added for clarification, but not found in the Greek or Hebrew. If you’ve ever learned any foreign language whatsoever, you’ll be aware that there are quirks between the two languages in how something is expressed. Russian, for example, has no “am/are/is” form – a subject noun followed by another noun or an adjective agreeing with the subject is a complete sentence, equivalent to “[The] ball [is] red.” Spanish often omits 1st person and 2nd person familiar pronouns, using them for emphasis. “Soy Americano” but “Yo soy un hombre sinciero” – “I am an American” but “I am an honest (sincere) man” – the beginning of the Jose Marti poem that furnishes the lyrics to Guantanamera. In the second sentence, there’s a slight emphasis on the subject – “I’m an honest man” so the pronoun is used.
There are great quantities of such instances in Scripture. In the verse so beloved of Biblical inerrantists, “All scripture is inspired of God and is profitable for teaching…” (II Timothy 3:16), the two usages of “is” are supplied – the verse is actually a long appositive characterizing the scriptures Timothy has known since he was a child, i.e., the Tanakh (Old Testament), and not the statement it appears to be in English at all. Another example is in the last verse of Matthew 4: “And there followed him great multitudes of people from Galilee, and [from] Decapolis, and [from] Jerusalem, and [from] Judaea, and [from] beyond Jordan.” In the original Greek, the case ending of Decapolis, Jerusalem, etc., makes it clear that they’re in parallel to “from Galilee,” but in English making one lone “from” carry five objects joined by “and” produces an awkward construction, so King James’s men supplied a matched set of "from"s for clarity. And there are any number of instances where the verb form clearly implies who among the previously mentioned people is the understood subject (female, singular – must be Ruth, not Boaz [m] or the crowd of kinswomen [f pl]), but English syntax requires either a “she” or a repetition of “Ruth” to make it clear.