What does the slash (/) mean in IP address allocation?

This is probably very much a newbie questions...

When people have talked to me about IP address range allocation they have discussed IP's with the use of a slash on the end of them, eg:

192.168.0.1/25 or 192.168.0.1/30

What does this /25, /30 mean on the end of IP addresses?

I am going to set-up a couple of servers soon, and the network admin mentioned what do I want as far as IP addresses go. They started talking about allocations that use this slash (/). Basically, I want 30 individual IP addresses that I can bind across 3 servers (10 per server). What should I be asking?

Are there any basic networking tutorials online that can help me understand this type of 'network talk'?

Thanks

The slash is how many subnet mask bits to use. since the use of classless routing you use slash instead of saying class A or B whatever. example..

192.168.1.1/24 is 192.168.1.1 255.255.255.0

255.255.255.0 is using 24 of the 32 bits to create the subnet.

in binary it looks like this..
11111111.11111111.11111111.00000000

so a /30 would look like
255.255.255.252 or in binary
11111111.11111111.11111111.11111100

the remaing 00 is for hosts the 1's are the network

Thanks juniperr

Juniper is correct. The term for this is CIDR.