A softening word used mainly by teenagers who are not entirely confident about the content of their speech. Used when they want to avoid an outright opinion or statement of fact that they might be challenged over or that someone might take offence at.
It can also be used along the lines of "You know what I'm saying?” to re-enforce the bond between speakers. With each use of 'like' requiring a nod from the listener to indicate they agree with the speakers assessment of events.
By opening any statement with 'like' the speaker can avoid responsibility for it being entirely true or not.
When overused (as it often is) it can be very annoying to listen to because it sounds like the person is not really saying anything of substance.
"...so I was like, so angry about it."
Rather than, "I was so angry."
"It was like, the best thing ever."
Rather than, "I thought it was the best thing ever."
"I'm like totally over him, and I like don't ever want to see him like, ever again. I mean like, what the hell? He's like a total sleaze"
Rather than, "I'm totally over him, and I don't want to see him ever again. I mean, what the hell? I think he's a total sleaze. Don't you agree?"