Answer:
What word starts with 'E', ends with 'E', but only has one letter? It is not the letter 'E'.
With head without hair. With mouth without tooth.
A great mysterious place that the bold have been known to journey into.
I drift forever with the current down these long canals they’ve made, Tame, yet wild, I run elusive Multitasking to your aid. Before I came, the world was darker, colder, sometimes, rougher, true. But though I might make living easy, I’m good at killing people too.
Different lights do make me strange, thus into different sizes I will change.
People take me on walks and I run and have fun. What am I?