Types of memory meaning [duplicate]

This question already has an answer here:

• What is the exact meaning of Runtime.getRuntime().totalMemory() and freeMemory()? 5 answers

I have a Java function that returns this :

Free memory: 56 651
Allocated memory: 298 496
Max memory: 901 120
Total free memory: 659 275

here is the function :

public String MemInfo() {
        NumberFormat format = NumberFormat.getInstance();
        StringBuilder sb = new StringBuilder();
        long maxMemory = runtime.maxMemory();
        long allocatedMemory = runtime.totalMemory();
        long freeMemory = runtime.freeMemory();
        sb.append("Free memory: ");
        sb.append(format.format(freeMemory / 1024));
        sb.append("<br/>");
        sb.append("Allocated memory: ");
        sb.append(format.format(allocatedMemory / 1024));
        sb.append("<br/>");
        sb.append("Max memory: ");
        sb.append(format.format(maxMemory / 1024));
        sb.append("<br/>");
        sb.append("Total free memory: ");
        sb.append(format.format((freeMemory + (maxMemory - allocatedMemory)) / 1024));
        sb.append("<br/>");
        return sb.toString();

    }

I want to know the meaning of each information and the relation between "free memory" "allocated memory" "max memory" and "total free memory"

PS : i want to do some charts with those numbers !