Who is the Doctor?
The Doctor is a time lord, the last of his kind. He regenerates from form to form and has lived for thousands of years.
As the Doctor is a time lord, he travels time and space. However he can't just do this on his own. He needs to use his TARDIS, which stands for time and relative dimensions in space
The doctor hates to travel alone. He takes someone along with him. His companions are normally human girls but can occasionally be male, or robot dog.
The Sonic Screwdriver
The sonic screwdriver is the one and only tool for the doctor. It does pretty much everything that is convenient to the plot. However its original purpose is to open doors but does not work on anything wooden.