Health insurance is a type of insurance coverage that pays for medical, surgical, and sometimes dental expenses incurred by the insured. On the other hand, life insurance is a contract between an insurer and a policyholder. The insurer guarantees payment of a death benefit to named beneficiaries upon the death of the insured in exchange for premium payments. 

A health insurance policy is a contract between you and the insurance company. You pay a monthly premium, and in exchange, the insurance company agrees to pay part of your medical costs, such as doctor visits, hospital stays, medications, and surgeries. Typically, you are also responsible for other costs like co-pays, co-insurance, and deductibles. 

Life insurance is particularly important if you are the primary breadwinner for your family or have significant debt. It provides financial security to your dependents in case of your death. The death benefits from a life insurance policy can be used to pay off debts, cover funeral costs, pay estate taxes, or provide a nest egg for your dependents’ future needs. 

Pre-existing medical conditions can affect both types of insurances. For health insurance, thanks to the Affordable Care Act, insurance companies can't refuse you or charge more due to pre-existing conditions (Only applies to Markeplace Plans). However, for life insurance, the presence of such conditions could potentially complicate the underwriting process or elevate premiums. In some extreme cases, an insurer may even decline to offer coverage.

Yes, you can purchase health insurance and life insurance policies from different insurance companies. This can be beneficial because it allows you to select specific plans that best meet your health and life insurance needs respectively.