Is it when someone babysits you because you can't manage your own money?
Basically yes. op.
I think a trust fund is where they give you a little bit of the money at a time so you don't spend it all.
A trust can be set up for a person who is too old or sick and then a bank takes over and pays all the bills and stuff and basically supervises all the money and makes sure the infirm person is taken care of first and that the heirs don't take all the money for themselves.
The deceased leaves the money to be managed by (usually) a bank, naming survivors who share in the gain on the principal each year, via stock trading and/or interest paid, but have no access to the money itself, except application for medical, legal, etc. expenses as outlined in the will.