Some English speakers, especially younger ones, use "you know?" on the end of their sentences. There's not a lot of meaning to it, but people use it when they want the listener to agree with the feeling or emotion of what they're saying. For example:
In this example, someone doesn't want to go to a party, but she feels like she has to. She wants the listener to agree with that feeling, so she says "you know?" at the end of the sentence. Another example:
There are some people who over-use "you know" and put it in almost half of their sentences. It doesn't sound very intelligent when you do this.
When someone who's speaking to you says "you know?", it's good to nod your head or say something like "Yeah."