I was reading the Wiki article on Hilbert systems and came across this passage:
A characteristic feature of the many variants of Hilbert systems is that the context is not changed in any of their rules of inference, while both natural deduction and sequent calculus contain some context-changing rules.
What does this mean exactly?
Does a "context" in a Hilbert system refer to the set of assumptions/non-logical axioms we are building our proofs from in the first place?
For example if we have some proof starting off with $\Delta \vdash \ldots \,$ then we can basically use $\Delta \vdash$ in front of every line of our proof. Is this our "context" and is this what they mean by "it never changes"? And in ND we are able to change contexts?
What does this refer to exactly?