A lakh signifies the number 100,000 and is used especially when talking about a sum of 100,000 rupees. For example, one might say "50 lakhs of rupees" to talk about 5 million rupees.
A crore signifies the number 10 million and is also typically used in discussing rupees. For example, one might mention "5 crores of rupees" when talking about 50 million rupees.
The South Asian numbering system is typically used in India, Nepal, Pakistan, Bangladesh and Sri Lanka.Learn more about Currency & Conversions