Spring OAuth2 security configuration

I am studying Oauth2 Security and I am really new to it. I found some issues when I go through several online documents and tutorials. Could anybody please help me to clarify following problems coz I was unable to clearly resolve those by myself even after searching through internet in the whole day.

I have used this link to set up test OAuth2 security application

<authentication-manager id="clientAuthenticationManager"
        xmlns="http://ift.tt/1c8inpe">
        <authentication-provider user-service-ref="clientDetailsUserService" />
</authentication-manager>  

<authentication-manager alias="authenticationManager"....

Q1. According to above xml code what is this clientAuthenticationManager and why is it used the alias authenticationManager ?

    <oauth:client client-id="restapp"
        authorized-grant-types="authorization_code,client_credentials"
        authorities="ROLE_APP"
        scope="read,write,trust" 
                    resource-ids=""
                    redirect-uri=""
        secret="secret" />

    <oauth:client client-id="restapp"
        authorized-grant-types="password,authorization_code,refresh_token,implicit"
        secret="restapp"
        authorities="ROLE_APP" />

</oauth:client-details-service>

Q2 What is client-id and for what purpose we use it?

Q3 What is this secret = "" what is the useage of it?

Q4 What is resource-ids="" what is the useage of it?

Q5 What is authorities = "" what is the useage of it?

Q6 What is redirect-uri="" what is the useage of it?

<oauth:resource-server id="resourceServerFilter"
    resource-id="test" 
    token-services-ref="tokenServices"/>

Q7 According to above xml code what is resourceServerFilter

Q8 What is resource-id="test" here.... for what purpose we need it?

Can anybody please help me to understand it......!