Separable Phrasal Verbs
A separable phrasal verb is called separable because the object can be separated from the phrasal verb (or not) depending on how it's written, but the general meaning remains intact no matter how you write it. One such phrasal verb is the expression 'hold up,' which means to delay. This can be expressed as one complete expression, as in, 'I had to hold up the meeting, because the office had disappeared' (in this case 'the meeting' is the object), or separated with the object between the verb (hold) and preposition (up), as in 'I had to hold the meeting up because the office had disappeared.' In both cases, the phrasal verb's meaning remains the same. If the meaning changes when you change the position of the object, the phrasal verb is not separable.
The one slight exception to this rule is when the direct object is a pronoun (I, you, me, we, he, she, it, they, et cetera). In this case, the pronoun that is the object must come between the verb and the preposition. There's no option of putting it anywhere else. As in, 'I've been meaning to look you up.' where 'look up' is the separable phrasal verb, and 'you' is the pronoun/object. 'You' must appear in between the two parts of the phrasal verb because it wouldn't make sense to say 'I've been meaning to look up you.'
Other separable phrasal verbs include expressions like 'back up' (to save a duplicate in case the original is lost or damaged), 'pay off' (to bribe), and 'throw away' (to waste something), among others.
Inseparable Phrasal Verbs
By contrast, inseparable phrasal verbs follow a similar format to separable phrasal verbs, but cannot be split up. Here are a couple of examples with the phrasal verbs in bold.
'I really wish that lizard boy would stop hitting on me.' 'Hitting on' is the idiom here, meaning, to flirt with, (this is an idiom precisely because what you don't do when flirting with someone is hit them - this is clearly a figure of speech), while 'me' is the object. This phrasal verb is inseparable because putting the object between the verb and its preposition would alter its meaning.
For instance, 'I really wish that lizard boy would stop hitting me on' suddenly makes no sense.
Other inseparable phrasal verbs include expressions like 'look after' (which means to care for), 'run for' (to campaign, like as for a political office), 'go through' (to use up, as in 'Elijah could go through all of his allowance in a day.'), 'get away with' (not be discovered or punished) and 'get along with' (have a good relationship with), though there are, of course, many more.
Intransitive Phrasal Verbs
Intransitive phrasal verbs are a little bit of a different beast from the other types we've discussed. Like other phrasal verbs, these usually consist of a verb and an adverb or preposition. Unlike those we've discussed before, intransitive phrasal verbs are not followed by a direct object, though they can be followed by an indirect object. For instance:
'This will all blow over,' Rachel said, watching Jeff's father's prized Lamborghini disappear into the ocean.'
The intransitive phrasal verb here is 'blow over,' which in this context means it will ultimately not do permanent damage (presumably to Jeff's relationship with his parents). As you can see, it doesn't require an object to make it work; the expression has meaning on its own. Let me give you a few other examples of intransitive phrasal verbs:
'The driver of the 1960s Mustang was a total show off.'
'Alice had to check out before she left.'
'My little sister always talks back to me.'