Here you are going to see the iPhone Keyboard Settings starting off with a number of different switches that you can set to the On or Off positions. The first one will be the Auto-Correction feature, which is a common annoyance among iPhone users.
The reason that this is a problem is that it often does not recognize words or will disturb your typing process. If you feel this is an interruption, or if it is simply not something you ever use, go ahead and turn it off. The same is true of the Auto-Capitalization function. Since you rarely use proper grammar and spelling online or in text messages, the Auto-Capitalization function may not help you. If you prefer to remain formal you can keep it, but it is often easier to manually capitalize than to utilize the iPhone Auto-Capitalization feature.
After the Auto-Capitalization will be Caps Lock, which is set to off by default. You should probably keep this off unless you are doing large volumes of typing, and this may also make you want to maintain the iPhone Auto-Correction and Auto-Capitalization. After this is the period shortcut, which applies a period if you space twice. This is rarely intrusive, so there is little reason to turn it off.
The last option in the iPhone Keyboard Settings is one to select an International Keyboard. This is not useful usually if you use American English, but there are several dozen other languages and dialects that you can use a keyboard for.