What do each of these features do exactly in myBB?

[SaturnElite]

• Enable search engine friendly URLs?
• Use GZip Page Compression?
• Send Standard Headers
• Send No Cache Headers
• Friendly Redirection Pages
• *NIX Load Limiting
• Output template start/end comments?
• Enable XMLHttp request features?
• Use PHP's Shutdown Functionality
• Advanced Stats / Debug information
• Uploads Path
• Use Error Handling
• Error Logging Medium
• Error Type Medium
• Error Logging Location
• Enable Forum Jump Menu?

[Livewire]

Moving to Scripts/3rd Party Apps as this is MyBB related and not related to issues with your free hosting account.

[carl6969]

You might find these links useful:

MyBB Wiki

MyBB Community Forums

[lemon-tree]

Enable search engine friendly URLs?
Use GZip Page Compression?
Send Standard Headers
Send No Cache Headers
Friendly Redirection Pages
*NIX Load Limiting
Output template start/end comments?
Enable XMLHttp request features?
Use PHP's Shutdown Functionality
Advanced Stats / Debug information
Uploads Path
Use Error Handling
Error Logging Medium
Error Type Medium
Error Logging Location
Enable Forum Jump Menu?

Most of these are just assumptions based on what the name suggests, but they are likely within the correct region. If I know I am likely to be way off then I have just marked it with a '-'.
1. Turns urls like index.php?page=home to URLs such as /home, this works better with search engine submission.
2. Compresses the page on load, this means less data is sent from the server but the page remains the same. However, this also uses CPU in the compression stage.
3. -
4. Do not force a cache time, this means the the user's browser can determine how long to maintain the cache for or whether to maintain one at all for the specified page.
5. If you move a page, this should how a nice message such as 'You have entered the incorrect address, we will now forward you to the correct one'.
6. Prevents the script from monopolising resources by limited the amount of server resources it can use.
7. -
8. Allows for asynchronous loading of content, meaning the page doesn't have to reload to load in new content.
9. -
10. Defines where uploaded files are stored
11. Lets you define what the server should do in the case of an error
12. -
13. -
14. -
15. Shows a little drop down menu to let you skip between forum categories. This forum has one titled: Quick Navigation
10. Allows you to see more in depth information about usage etc