What does setting a time zone on Google Calendar actually achieve?

What does setting a time zone on Google Calendar actually achieve?

I'm currently in GMT+1, and have just created a calendar with a GMT-5 time
zone. If I add a new event to this calendar, it is created with my current
GMT+1 time zone. To create an event at GMT-5, I have to specifically set
the new event time zone to GMT-5 when I create it. It will then be shown
adjusted to GMT+1.
But if I have to specifically set the time zone of every event I create in
this new calendar, then what's the point of setting the calendar time zone
to GMT-5 in the first place?