Please, what are are trading signals, how do they work and are there real trading signals? Someone said all are pump & dump game, how true is that?

I have majorly been a Poloniex user, tried Binnace but don't like the limit there, it prevents you from trading micro amount of coins and leaves you with a whole lot small pieces of coins you might not want to hodl for a longterm.

I have recently been considering COBINHOOD, which claimed to be a no fees exchange, so please what is your experience with COBINHOOD?