Invitations & Connecting
Connecting to someone on LinkedIn implies that you know them well:
They’ll have access to people you know
Others may ask you about them and vice versa
You’ll get updates on their activity
LinkedIn lets you invite colleagues, classmates, friends and business partners without entering their email addresses.
However, recipients can indicate that they don’t know you. If they do, you’ll be asked to enter an email address with each future invitation.