A lakh is one hundred thousand and a crore is ten million. The Indian numbering system groups digits differently from the international one, which is why 50,00,000 and 5,000,000 are the same number written two ways.
One lakh is 100,000 - one hundred thousand. Written with Indian digit grouping it appears as 1,00,000.
One crore is 10,000,000 - ten million, or one hundred lakh. Written with Indian grouping it is 1,00,00,000.
The international system groups digits in threes throughout - 5,000,000. The Indian system groups the last three, then in twos above that - 50,00,000. Both describe the same quantity; only the separators move.
Ten. One million is 10 lakh, and one crore is 10 million. A billion is 100 crore.
Yes - they are standard in Pakistan, Bangladesh, Nepal, Sri Lanka and Myanmar, covering well over 1.7 billion people between them. Property, salaries and government budgets across the region are quoted this way.