It maps an input — a nickel — into an output — a slot for nickel.Activation function basically acts like the sorting machine, it takes an input and maps it to an output..The coins has a flat surface with dollar sign and a real number written on it.$239$0$-1129$3.14$-1.41…She needs to use valuable coins to purchase something, and it seems like the coins that is scattered on the floor each has different values..Sorting the coins into valuable and not valuable coins would take hours, so she decides to buy a machine that can help her do that.Sigmoid coin sorterThe next day, the coin sorter has arrived in her mail..It has a 0.1 increment on each slot*.She reads the manual and discovered that this machine can tell how valuable a coin is, which is represented by the number on the slot.The closer a coin gets to 1.0 slot, the more valuable the coin is according to the machine.If a coin falls into the slot of 0.9, the machine is 90% sure that the coin is valuable.She took 3 random coins and put it in to see how it works.The first coin, which has value $-1.32, falls into the 0.2 slot.The second coin, which has value $-9001, falls into the 0.0 slot.The third coin, which has value $51025, falls into the 1.0 slot.She realized that by only taking the coins that falls into the 1.0 slot, she can put the most amount of dollar in her pocket..This realization brings a huge smile on her face.Amy pour all her coins into the machine, and takes the coins on the 1.0 slot.She opens the door with pocket full of valuable coins, ready to shop.PS*: The result of sigmoid is actually continuous value ranging from 0 to 1..The slot mentioned above is illustrated as discrete for the sake of simplicity.What the does coin represents?Amy’s coin represents a linear combination— the feed forward process — of a neural network until the last layer.The result of a linear combination can be any number..That’s why Amy’s coin is illustrated as such.The coin sorter mentioned above takes a coin and put it to a slot between 0 and 1.. More details