Grandmother trust fund can't reach it until 22 years old? Unsure. Help read.

Grandmother said to me she holds money for me but I can't do anything until I turn 22 years old.
I am the benif.
I'm unsure what kind of thing she is talking about here. If it is a trust or something else. She has a will and gets a check for herself every month from social security. She told me once she passes away I get other money but now at 22 I obtain this first.
I just would like to know what she could have set up for me.
Thanks.