Older homes often have two-prong outlets with no ground wire. They work, but the missing ground removes a layer of shock and surge protection, and they can't safely power equipment that needs grounding.
Why grounding matters
The ground gives fault current a safe path and protects sensitive electronics from surges. Without it, a fault can energize a device's metal case, and surge protectors can't do their job properly.
Your options
The best fix is running a proper ground, but that can mean rewiring. A common code-permitted alternative is replacing the outlet with a GFCI, which protects against shock even without a ground (it must be labelled 'No Equipment Ground'). Important: this is a shock-safety fix only — it does not actually ground the outlet, so equipment that genuinely needs a ground (and surge protectors) still isn't grounded. An electrician can advise the right approach for your wiring.
Don't cheat it
Never use a cheater plug to force a three-prong device into an ungrounded outlet without GFCI protection — it defeats the safety the ground pin provides.