The terms "long
position" and "short position" refer to the two sides of a trade
entered by two or more parties. A long position is simply defined as the
purchase of a security, stock, currency, or other commodity with the
expectation of making a profit, while a short position refers to the situation
in which a trader sells a security or other commodity with the intention of
later repurchasing it at a lower price.
Source: https://www.wallstreetmojo.com/long-and-short-positions/
A long position indicates that the investor has purchased and acquired the stock shares in question. A short position, on the other hand, indicates that the investor owes someone money for those stocks but does not yet possess them.
For instance, an investor is long 100 shares if he or she has 100 shares of Tata Steel in their portfolio. The cost of owning the shares has been fully paid for by this investor.
The term "short 100 shares" refers to an investor who sold 100 Tata Steel shares but has not yet acquired those shares. At settlement, the short investor owes 100 shares and is required to repay the debt by getting the shares from the market to deliver.