A lakh (/ˈlæk/ or /ˈlɑːk/; abbreviated L; sometimes written Lac or Lacs) is a unit in the Indian numbering system equal to one hundred thousand (100,000; scientific notation: 10^5). In the Indian convention of digit grouping, it is written as 1,00,000. For example, in India 150,000 rupees becomes 1.5 lakh rupees, written as ₹1,50,000 or INR 1,50,000.
It is widely used both in official and other contexts in Bangladesh, Bhutan, India, Myanmar, Nepal, Pakistan and Sri Lanka. It is often used in Indian, Pakistani, and Sri Lankan English. In Pakistan, the word lakh is used mostly in local languages rather than in English media.From Wikipedia based upon an encounter with it here.
Another notable insight, from the same source, is this: "The word lakhi is commonly used throughout Tanzania to denote 100,000 shillings and is likely to have entered the Swahili language from Indian and Pakistani immigrants."
A related term is Crore (= 100 lakh = 10 million).