You can sign in with a Facebook or Google account instead of a password. Manage this under Settings → Account → Security → Login Methods.
Linking one
Select Link next to Facebook or Google and complete the sign-in. Both can be linked at once.
After that, either appears on the login screen under or continue with.
Why do it
One less password. Nothing to remember.
A backup route in. If you lose your password, a linked account gets you in without a reset email. Genuinely useful if you have an event coming up and a balance to pay.
What it doesn't change
Linking doesn't create a second DJfindr account. Your password, Facebook, and Google sign-in methods are interchangeable ways into the same account.
Your email address stays your primary identifier.
Which account to link
One you'll keep and control long-term. Linking a work email you'd lose if you changed jobs defeats the point.
If you signed up with Facebook or Google
You may not have a password at all. Setting one from Settings → Account → Security gives you a second way in, which is worth doing.
Security
If you turn on two-step verification, you'll enter a code after every sign-in, including one through a linked account. See Setting Up Two-Step Verification.
Unlinking
From the same Login Methods section. Make sure you have another way in first — a password set, or the other provider linked.