Answer: Hello mate!
We know that you have a graph of y vs t, and we know that this is an "altitude" graph.
Then we can assume that the y represents the altitude, and t represents the time, and this graph shows the altitude of something as a function of the time.
the t-intercept means that the graph passes through the y-axis, this means that, in this point, y is equal to zero:
Then, at the t-intercept, we have y = 0, which means that at this time (where is the intersection) the altitude is equal to zero.
The y-intercept means that the graph passes through the y-axis, where t = 0
this is the initial value of the altitude, where t = 0 usually denotes the time where we start to measure.