Subnet Mask divides the IP address into two segments and informs the computer which part is the network bit and which one is the host bit. For example, if there is an IP address: 192.168.0.1, it will ...

So, for example, if I have a VPN road warrior set up, and I'm somewhere where the network is 10.0.0.1/24 but the VPN tunnel network happens to be 10.0.0.1/30? Changing the client network address is ...

As Drizzt figured, your problem is that the two remote networks have the same LAN subnet. Change the other side to use 192.168.2.0/24, or literally any other subnet so it doesn't collide/overlap with ...