Beneficiary
The person(s) who will inherit your Assets / Money
Executor
The person(s) or institution that ensures that your wishes are carried out according to your will. This may be any person older than 18 years. Preferably someone who will inherit more than 50% of your estate.
Trustee
The person(s) or institution that ensures the correct distribution and safe keeping of the assets of your minor beneficiaries until they reach a certain age, as stipulated by you.
Gaurdian
The person(s) who will be taking care of your children, thus essentially becoming the new 'parents'.