I received an offer for an alumni term group life insurance plan. A 10 or 20 year plan with coverage from $100,000 to $1,000,000. (level premiums, guaranteed to age 75)
If I don't die within the 10 or 20 years what happens when the policy matures?
Do I get the $100,000 (if that is the term I choose) or some other amount of money?
Or does it go to the beneficiary?

I am 48, in good health, the youngest in my family and if I outlive the others so can this be considered an investment for myself?

"If I don't die within the 10 or 20 years what happens when the policy matures?" Wow, you do need to learn about level Term Life. The policy doesn't mature, it expires. You get nothing with term, that is why it is so cheap. The only time a beneficiary would collect under term life is if you die. Life Insurance is never an investment for yourself, it is for someone else. Whole life does have cash options but not level term.

No, this type of policy does not mature. If it is purely a term life policy, nothing happens if you live, at the end of the 10 or 20 year, the policy ends and the insurance companies keeps the money paid in. No one gets money if you live.

There are some "term" policies that have a cash investment attached. (100s of names for them) in those cases, the money you pay into the policy, minus the cost of the term insurance can grow as an investment.

But if this is purely a term policy, they are very low cost, because, they only pay if you die.