An opening dictates how you are going to start the match.
The basic Zerg openings:
- 6–10 Pool (Rush)
- 13–14 Pool (Standard)
- 14–15 Pool, 16 Hatch (Macro)
- 14–15 Hatch, 15–16 Pool (Macro+)
- 14 Gas, 14 Pool (Speedling)
- 12 Pool (Sen Style)
How to read these: The number indicates the number of drones you should have before your first structure. Since you can only build 10 before an overlord any number over 10 indicates building an overlord on 9 or 10 (9 or Extractor trick is the superior choice). Pool indicates building a Spawning Pool. Hatch indicates building a Hatchery. Gas, indicates building a Vespene Extractor on your nearby Vespene Geyser.
Which opening you choose usually relies on two things:
- Your Opponent
- Your Build
The Rush: A Rush opening is necessarily an all in, so that is a decision you are making prior to starting the match.
Standard: 13–14 pool is considered standard play, it can easily lead to fast expo or 1 base or speedlings or any of another things. It's considered standard play because of the options it offers you. I believe Slush of Root Gaming still runs this build.
Speedling: This is a strat that cropped up near the end of Beta mostly on Korean servers. If you build your gas before your spawning pool and immediately throw 3 drones in it on completion, then you will have exactly 100 gas when your spawning pool finishes. This leads to early speedlings for heavy pressure. Artosis is a large proponent of this build.
Macro and Macro+: Both of these are fast expansion builds designed to get up a very good early economy. They are very vulnerable to rushes, and require good scouting to support. The advantage of these is that if you can scout when your opponent leaves his base you can quickly put together a large force that will be ready just as he arrives allowing you to hold off the assault and be in better economic position. Idra and Machine tend to run this build.
Sen runs a 12 pool to give him a larger advantage against more aggressive zerg opponents, which are common on the asian server. Outside of him, it is not a very popular build.
9 Overlord vs 10 Overlord
There has been a lot of debate as to getting your overlord after your 9th drone or after your 10th drones. To add confusion it is possible to get your overlord after your 11th drones by building a vespene extractor, building the 11th drone and then canceling the extractor to get your drone back. It is usually agreed that getting your Overlord on your 9th drone, or building it after your 10th and then using the extractor trick to get an 11th while your overlord is building are the better choices.
There is some evidence to indicate 9 overlord is slightly better.
I first wrote this post shortly after beta and while most of what I wrote here still rings true there has been a shift in the Meta game in that time. While 13–14 Pool is still an effective strategy, many more Zerg have shifted towards more Macro oriented builds. 14–15 Hatch in particular has really caught on in ZvT. Everything in the post remains valid but I think it's still worthwhile to update on some of the newer developments.
Best Answer
Normal background, it just helps you put things in perspective of the map. I don't think I've seen any top level players use a black background.
Most players prefer setting enemy units to red on the minimap, this helps to alleviate your issue with seeing them against the backdrop. This sets ally units to yellow and your own units to green no matter what your actual colors are. I believe the command to do so is Shift+Tab.