It wasn't ACTUALLY low-budget- it was BBC budget. Which is low by default, but relatively speaking it was middling...
It will probably be much more budgeted this time around- especially for only 6 epiosdes (back in the sixties, series went on for some 40 weeks).
There have been eight Doctors, curly haired guy was Tom Baker, number four. That tv movie was the 1996 screening I referred to and starred Paul McGann as the Eighth Doctor, whom I mentioned above.
Asking what Doctor Who is about is a tricky question as its concept was almost infinitey extendable- you could write stories about virtually anything. Over its 30 year run it went though all sorts of phases and has had a great mix of the classically brilliant and the utterly shite.
But the BASIC premise is this. The Doctor (a title he assumes as his name is rather obscure) is a being from the planet Gallifrey, part of a race called the Time Lords- so called because they have complete mastery over the science of Time Travel. Their millions of years old civilisation is, however, rather static and somewhat decaying, The Doctor is unusual for a Time Lord as he has a great curiosity about the Universe so he left, in a stolen ship, to explore it- something that makes him an outcast. And for the first few decades of his time away from Gallifrey he settled on Earth in the 1960s whilst trying to fix the ship (he stole a broken one). As a result he gained an appreciation for the human species (whom he, of course, physically resembles)
The Doctor, coming from a highly advanced alien race, knows tons about everything and is the perfect scientist. He is also kind, friendly, good-humoured, rather eccentric- and hates all forms of evil. His ship is actually a 'TARDIS ('Time and Relative Dimensions in Space'😉 and is less of a ship and more of a portable 'reality' in which he can travel around throughout space and time (though he can never quite steer it correctly). It extends into the real world in a physical manifestation which contains a device designed to make it blend in with its surroundings when it 'lands (it does not fly like a normal ship- it materialises into the real world next to things), so if it materialised next to a bunch of rocks it would look like another big rock- but with a door built in that took you into the TARDIS which is far bigger on the inside than out, its physical maifestation being only a gateway.
Unfortunately for the Doctor his chameleon circuit is knackered. When he landed on a junkyard in London in the 60s the TARDIS took the look of a London Police Box- and then got stuck. No now matter where he goes in space and time, his TARDIS always looks like a Police Box and sticks out like anything.
So then- in each story, the Doctor goes somewhere, anywhere in the universe and anywhere in time, and he normally finds something bad going on which he helps sort out, accompanied by companions he has picked up along the way who travel with him for a while before leaving. And that is the set-up- this slightly mad but incredibly capable scientist with a time machine goes anywhere sorting out stuff. Because he likes humans, a large amount of his stories are about about helping out Earth- whether in Roman times, Victorian times, Modern times, or the far future.
The last twist is this- the Doctor's race has 13 'lives'. When the Doctor is killed- as occasionally happens- he can regenerate into a new form (which basically meant the actor was done doing the role and someone else was due to take over). The new Doctor is similar in basic personality but the details are often very different indeed. Some of the most amusing Dr. Who stories are the ones when the Doctor meets a past version of himself- they always hate each other.
And yeah- that is Dr. Who!