SOCKS servers are a form of proxy that are commonly used
in firewalled LAN environments to allow access between networks,
and often to the Internet.
The problem is that most applications don't know how to gain
access through SOCKS servers.
This means that network based applications
that don't understand SOCKS are very limited in networks they can reach.
An example of this is simple 'telnet'.
If you're on a network firewalled from the internet
with a SOCKS server for outside access,
telnet can't use this server and thus can't telnet out to the Internet.

tsocks' role is to allow these non SOCKS aware applications
(e.g telnet, ssh, ftp etc) to use SOCKS without any modification.
It does this by intercepting the
calls that applications make to establish network connections
and negotating them through a SOCKS server as necessary.