You need to know:
1) When it began
2) Where it was
3) Key people involved
When did the first tube line open?
On 10 January 1863, the Metropolitan Railway opened the world's first underground railway.
Where was the first tube line?
It was built between Paddington (which was called Bishop's Road at that time) and Farringdon Street.
Key people involved:
Sir Marc Brunel and his son Isambard built the world’s first underground river tunnel- the Thames Tunnel in 1843 (which is now part of the London Overground). This inspired others to design and create the tube system for passengers.
In 1933, a man called Harry Beck created the first tube map as we know it today.