lag comes from the servers,not from steam
Lag can come from any of three places:
1 - the server machine not being able to cope with the load.
2 - the connection between oneself and the server not passing packets quickly enough.
3 - one's own machine not being able to receive & understand packets quickly enough.
All three of resulting from either inefficient technology (not enough CPU/RAM, or bandwidth), or over-used technology (too many players/users).
But I'm guessing mole probably means the amount of time it takes to sign-in to Steam/etc.