Hi,
Regarding Martingales you an can see them as fair games This means that if the (martingale) process represents your gain(random) wealth, you should not be able to design a strategy to increase your current gain wealth, no matter what the outcome of the sample space is. And this property is stable.
Brownian Motion can be seen as a limit of rather simple random walks but I m I'm sure that you know about this.
Markov processes "disconnect" Future and Past of the process conditionnally on the present value of the process. Where disconnect "disconnect" means that functions of past and of future values of the process are independent condionnally conditionnally on the present value of the process.
Does it make things more clear ?

