In this thread, the top answer discusses: "buy on bid, sell on ask" as "market making" strategies.

My question is:

1. In layman terms, what does "buy on bid, sell on ask" mean?
2. Why are these techniques called "market making"?
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FYI, that answer has things reversed. Market makers buy at the bid and sell at the ask because they are passive traders. Buying at the ask, or lifting the offer, means you are aggressively taking liquidity and crossing the spread. –  Louis Marascio Oct 25 at 11:59
You're going to attract a lot of negative attention by asking for "laymen's terms" definitions of simple concepts. This site is meant for professionals who practice quantitative finance on a daily basis. –  Joshua Ulrich Oct 25 at 20:09
@LouisMarascio Wow...I didn't even notice that was reversed. That's insane. Would be nice if everyone did a little googling before asking a question. –  Shane Oct 26 at 1:47
@Shane I've already suspended this user. In the span of one day he's asked how stock prices are determined, what the limit-order book is, and how HFT adds to liquidity. –  chrisaycock Oct 26 at 2:14

## closed as off-topic by kurast, olaker♦Nov 1 at 14:52

This question appears to be off-topic. The users who voted to close gave this specific reason:

• "Basic financial questions are off-topic as they are assumed to be common knowledge for those studying or working in the field of quantitative finance." – kurast, olaker
If this question can be reworded to fit the rules in the help center, please edit the question.

Most organized markets have intermediaries to match buyers and sellers who may arrive at different rates. These intermediaries are typically called market makers because they "make markets" by buying from people who want to sell and selling to people who want to buy.

Since market makers take on risk to provide liquidity, they generally need to be compensated for their services. This compensation usually comes in the form of what's called the "bid/ask spread". A market maker will buy at the bid price and sell at the ask (or offer) price. These liquidity providers can thus earn a return by providing immediacy to impatient traders.

See Harold Demsetz (1968) "The Cost of Transacting" for an early reference on this subject.

There is an extensive field to explain this field known as "market microstructure". As I discussed in the past, there were traditionally two major types of models for explaining the spread within this literature: asymmetric information based models and inventory models. Inventory models were originally derived from Garman (1976). Asymmetric information models have received the most attention recently; there are two standard frameworks: the "sequential trade framework" by Glosten and Milgrom (1985) and the "strategic trade framework" developed by Kyle (1985).

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