Auto insurance policies vary, especially the exclusions area, so it would be up to the specifics of your policy if someone you loan your car to will be covered or not by your current policy.
In general, most insurance policies will extend your coverages to those that you give permission to operate your vehicle however if that person lives in your household then they would normally have to be on the policy to be covered and if you loan your car out to a friend for an extended period of time or a person drives your car on a regular basis they may need to be added to the policy as an occasional driver.
Some policies have exclusions for other drivers though. The exclusions may only allow the listed drivers to be covered or more likely exclude drivers under a certain age (i.e. under 25 years of age).
If your car insurance policy covers others that you allow to drive your car than normally both your liability and collision coverages will cover an accident that the friend may be in. The person would not be covered under your uninsured motorist coverages, those are for when an uninsured motorist would cause harm to you in an accident, not if your driver is "uninsured," meaning in this context that he or she did not have their own policy covering them.
To find out what coverages from your policy would extend to anyone you allow to drive your vehicle, read through the terms of your policy and speak with your insurance company's agent. They should be able to explain what coverages extend to others that drive your car and what would happen if another driver operating your vehicle was in an accident. If your coverages extend to other drivers then normally claims would come through your policy for an accident and thus your future rates could be affected.
If your current insurance policy does not fulfill your needs or you are ready to shop around for auto insurance, click here to get affordable car insurance rate quotes.