When setting permissions for a filesystem to be mounted in fstab why do you have to use 4 numbers in the umask. ex: umask 0000. I know what the last 000 do, they give wrx permission to the owner, group and other but what is that first number for. Maybe someone can explain quickly to me what it's for. Thanks!

First number is for the setuid, setgid, and the sticky bit. Example:
You know the last numbers work like this:
4=r,2=w,1=x. 'rwx'=7, 'rw-'=6, 'r--'=4. Thus you have the three numbers, '777', which means 'rwxrwxrwx'.
The first digit is similar, I think it goes like this; 4=setuid, 2=setgid, 1=sticky bit
setuid: if this is enabled, then the program is run as the same user as the user who owns the file
setgid: if this is enabled, then the program is run as the group that owns the file
sticky bit: cache this file in the swap, not used for what it was meant for anymore, sometimes used for other things

how is setuid, setgid and stick bit used. Give me an example of when you would use it.

For example, if regular users needed to run a program as root: the setuid would be enabled on the program file, and the program would be owned by root. Then the program can be run as root by anyone.

The sticky bit is something old. It once ws meant for caching files in the swap. For example, if a program had the sticky bit enabled, the kernel would keep it in swap, supposedly for faster access. It doesn't do this anymore, and the sticky bit is ignored on files. On folders, however, it has a completely different function that still works (search it).

Thanks!