Evaporation, in ELI5 terms, is simply a molecule of water getting so excited that it literally jumps out of the container in which it is stored.

A puddle of water contains a bunch of water molecules which are all bouncing against each other and their container, but they don't have the energy needed to actually bounce out of the container. Then a (relatively) warm room or a little bit of sunlight provides some extra energy, and a molecule gains the extra energy needed to leap out of the puddle and into the air.

This can happen at any temperature above O C.

At temperatures below 0 C, as described in other posts, water molecules can skip the liquid phase and go straight from ice to vapor in a process called sublimation.

It all boils down (pun absolutely intended) to energy input.