Hi, indrajith,
All these concept are for the authentication purpose. i will try to explain each points
1. key−chain
You are making a keychain with name of MYCHAIN. in side of this key chain iu can make many keys .
Its like the bundle of your house key. each key bundle have many keys for different rooms or stores
2. key- one key from budle of keys
Each key can use for authentication . and u can specify wich period each key need to use
eg
key-1 mandy to friday
key 2 satuday only
key 3 sunday only
3. key-string
It is the simple password for the authentication ( can be clear test or MD5)
by
shiji varughese