A couple of days ago I gave a presentation on language to a local seniors organisation. They were a lively, opinionated bunch, which made the morning loads of fun. During the tea break, one woman whispered to me how much she hated her grandchildren's habit of using like as a filler (as in, "I was, like, so bummed out").
Let's get the terminology out of the way first. Like, used in that manner, is called a discourse particle. That's another name for a word that has no direct semantic meaning within the sentence in which it occurs.
But Beryl (not her real name) had no business getting righteous about the ringing emptiness of young people's speech. She certainly is just as guilty as her grandchildren of uttering meaningless words.
Don't believe me? Notice the next time you respond to a question with a sentence that begins "Welllll, ....". Let me tell you, that word well doesn't mean a damn thing. And if you never say "you know", well, you know, you're a better man than me, Gunga Din. I won't bore you with more examples, but trust me when I say the list is, really, pretty darn extensive as a matter of fact.
Discourse particles, which are recognisable words stripped almost bare of meaning, are a subset of fillers, which include sounds that never have lexical meaning in any context, such as your ums, ahs, ers, and so on. Whether they have no meaning at all is debatable. Some researchers say they're devices for giving yourself time to think about what to say next without ceding control of the conversation - a bit like slow drivers who hog the fast lane (but don't get me started). In that case, they certainly perform a meaningful function in speech. And if you're someone who likes to have the last, ah, word, it could be a very useful function indeed.