chore(docs): make clearer link between template and actual email (supabase#36712)

Author: avallete

apps/docs/content/guides/local-development/customizing-email-templates.mdx

@@ -32,13 +32,49 @@ content_path = "./supabase/templates/invite.html"
 
 ## Available email templates
 
-There are several Auth email templates which can be configured:
+There are several Auth email templates which can be configured. Each template serves a specific authentication flow:
 
-- `auth.email.template.invite`
-- `auth.email.template.confirmation`
-- `auth.email.template.recovery`
-- `auth.email.template.magic_link`
-- `auth.email.template.email_change`
+### `auth.email.template.invite`
+
+**Default subject**: "You have been invited"
+**When sent**: When a user is invited to join your application via email invitation
+**Purpose**: Allows administrators to invite users who don't have accounts yet
+**Content**: Contains a link for the invited user to accept the invitation and create their account
+
+### `auth.email.template.confirmation`
+
+**Default subject**: "Confirm Your Signup"
+**When sent**: When a user signs up and needs to verify their email address
+**Purpose**: Email verification for new user registrations
+**Content**: Contains a confirmation link to verify the user's email address
+
+### `auth.email.template.recovery`
+
+**Default subject**: "Reset Your Password"
+**When sent**: When a user requests a password reset
+**Purpose**: Password recovery flow for users who forgot their password
+**Content**: Contains a link to reset the user's password
+
+### `auth.email.template.magic_link`
+
+**Default subject**: "Your Magic Link"
+**When sent**: When a user requests a magic link for passwordless authentication
+**Purpose**: Passwordless login using email links
+**Content**: Contains a secure link that automatically logs the user in when clicked
+
+### `auth.email.template.email_change`
+
+**Default subject**: "Confirm Email Change"
+**When sent**: When a user requests to change their email address
+**Purpose**: Verification for email address changes
+**Content**: Contains a confirmation link to verify the new email address
+
+### `auth.email.template.reauthentication`
+
+**Default subject**: "Confirm Reauthentication"
+**When sent**: When a user needs to re-authenticate for sensitive operations
+**Purpose**: Additional verification for sensitive actions (like changing password, deleting account)
+**Content**: Contains a 6-digit OTP code for verification
 
 ## Template variables