All the vocalizations and tail movements you see among squirrels around food sources boil down to pretty much one sentiment: "Get away, this food is mine!" Squirrels do say other things, such as, "Get out of here, this land is mine" and "Don't even think about trying to keep me off that birdfeeder, because it's mine." It's like a two-year-old's credo: "What's mine is mine, what's yours is mine, what you came in with is mine, if I want it it's mine, if I don't want it it's mine...." Or those gulls in Finding Nemo: "Mine-Mine-Mine-Mine......"
No, seriously, squirrels do have many vocalizations and also communicate with their very expressive tails. Imagine what humans, with our wide range of emotions, might do with tails! Squirrels certainly don't have sophisticated conversations like we do (some of us, at least), and most of what they say can be classified either as territorial or alarm signals.