Full Idea
Hilbert's geometrical axioms were existential in character, asserting the existence of certain geometrical objects (points and lines). Euclid's postulates do not assert the existence of anything; they assert the possibility of certain constructions.
Gist of Idea
Euclid axioms concerns possibilities of construction, but Hilbert's assert the existence of objects
Source
report of David Hilbert (Foundations of Geometry [1899]) by Charles Chihara - A Structural Account of Mathematics 01.1
Book Reference
Chihara,Charles: 'A Structural Account of Mathematics' [OUP 2004], p.9
A Reaction
Chihara says geometry was originally understood modally, but came to be understood existentially. It seems extraordinary to me that philosophers of mathematics can have become more platonist over the centuries.