Given a function that has 3 arguments

sum = lambda x, y, z: x + y + z
sum(1,2,3) # sum 3 numbers

sum([1,2,3]) # error, needs 3 arguments, not 1 list

x = [1,2,3][0]
y = [1,2,3][1]
z = [1,2,3][2]
sum(x,y,z) # ok

sum(*[1,2,3]) # ok, 1 list becomes 3 arguments

Given a function that has 3 items as argument

sum = lambda x, y, z: x + y + z
sum(1,2,3) # sum 3 items

sum([1,2,3]) # error, needs 3 items, not 1 list

x = [1,2,3][0]
y = [1,2,3][1]
z = [1,2,3][2]
sum(x,y,z) # ok

sum(*[1,2,3]) # ok, 1 list becomes 3 items

Imagine this toy with a bag of a triangle, a circle and a rectangle item. That bag does not directly fit. You need to unpack the bag to take those 3 items and now they fit. The Python * operator does this unpack process.

Given a function that has 3 arguments

sum = lambda x, y, z: x + y + z
sum(1,2,3) # sum 3 numbers

sum([1,2,3]) # error, cannot assign 1 list to a function with 3 arguments

x = [1,2,3][0]
y = [1,2,3][1]
z = [1,2,3][2]
sum(x,y,z) # ok

sum(*[1,2,3]) # ok, same as above, simpler, * turns this list to x=1, y=2, z=3

Given a function that has 3 arguments

sum = lambda x, y, z: x + y + z
sum(1,2,3) # sum 3 numbers

sum([1,2,3]) # error, needs 3 arguments, not 1 list

x = [1,2,3][0]
y = [1,2,3][1]
z = [1,2,3][2]
sum(x,y,z) # ok

sum(*[1,2,3]) # ok, 1 list becomes 3 arguments