CodeIginter provides a number of security options to handle to our applications:
a. URL security
b, Global security
c. Filtering data
d. Password salting
e. Database security
f. Cross-site scripting

There is a number of email class functions available in CodeIginter:
$this->email->from()
$this->email->reply_to()
$this->email->to() 
$this->email->cc() 
$this->email->bcc()
$this->email->subject()
$this->email->message() 
$this->email->set_alt_message() 
$this->email->clear() 
$this->email->send() 
$this->email->attach() 
$this->email->print_debugger()

A CodeIgniter library is simply a class file that abstracts functionality into easy-to-use functions tha take much of the strain off the developer. The term "class" and "library" are used interchangeably in CodeIgniter.

A codeIgniter session is simply an array containing the following data:

1. The user's unique Session ID
2. The use's IP address
3. The user's User Agent string
4. The "Last activity" timestamp

Session ID: This is a randomly-generated number, which is hashed with MD5 for portability, and is regenerated every five minutes.