There are several server options that affect weapon damage in Team Fortress 2, and they're often confused:
Weapon Spread -- With this turned on, hitscan weapons, such as shotguns, will have the same non-random pattern of "bullets" each time they are used. Default is ON.
Damage Spread -- Each weapon normally has a minimum and maximum damage. No Damage Spread means that each weapon will do a set, average, damage rather than varying between attacks. Default is ON. (Critical hits always do 3 times damage)
Damage Falloff -- Normally, the damage dealt by a weapon decreases the farther away you are for your target. If this is turned off, A rocket detonating right next to you and a rocket shot from the opposite side of the map will do equivalent damage. Crits are never affected by Damage Falloff. Default is ON.
The default is to have Damage Spread ON. Nodmgspread refers to servers which have turned it OFF.
Once the 4th rax has finished, pull half your SCVs and poke his ramp with your marines.
Pulling means you take them away from what they are currently doing.
So, you pull half of your SCVs away from your resources, but to do what?
This is pointed out in the next sentences:
You can first place a bunker outside his ramp to give you micro space. Once you're up the ramp, build another bunker and start targeting workers. Make sure to keep producing from your barracks and making depots.
Basically, you send some SCVs along behind your marines so that they can build bunkers and repair those bunkers, the other SCVs you have pulled are useful for supply depots and taking damage.
Every time that a SCV dies instead of a Marine when you are pushing him, it's in your advance.
Why does this work? As you are solely producing marines that cost 50 minerals and placing some buildings that cost 100 minerals, you are able to work with half the mineral income and still have constant production running.
When Terran pulls SCVs, it is strongest against zerg; however Mega Rax is also the hardest to hide from zerg.
In contrast with other races, Zerg is the only race that needs to decide whether he needs to spent his larvae on workers or on army units, as he is under pressure he will need to produce more army units at the cost of his workers. So, if you pull SCVs which gets your economy down, your opponent his economy will also be down because of the pressure that you apply on his production...
Best Answer
You might want to take a look at Minecraft Wiki's article on server setup. They also have a very useful tutorial on setting up a server as well.
If you're wondering about something more specific, take a look at the article on the server.properties file, which explains how you can customize your server to fit your needs.
As for what exactly
server-ipdoes, it's unnecessary. You might as well leave it blank.