What is the difference between the joint probability $P(x_2,t_2;x_1,t_1)$ and the conditional probability $P(x_2,t_2|x_1,t_1)$ where $x_1,x_2$ are two values from the sample space of a random variable $X$? Here, $t_1$ and $t_2(>t_1)$ represent time.
It will be helpful to get an answer that will explain the meaning of these two probabilities in the example I wrote.
Joint probability describes the probability that two (or more) events both occur: What is the (joint) probability that I find the next car that passes is both red and a four-door model?
Conditional probability describes the probability of an event given that another event has occurred. What is the (conditional) probability that given the next car is in fact red that it is also a four-door model?