Doubt about heat and heat capacity(2nd semester-1st block-1st unit 1.4)

[SCP_ GYPSY_MAN]

On the definition, there are two aspects pointed out to note.

one, heat appears only on the boundaries of the system.

two, heat appears only during the change in the state of the system.

I have confusion on the first aspect. If I boil some water in a beaker, the beaker and water became heated, Then how can we say heat only appears in the boundaries of the system?