Hundreds of different companies' shares are traded on the stock exchange, but not all of them are equally popular among traders. Interest in a stock is influenced by its liquidity, which determines the value of trading costs on buying and selling.
In particular, liquidity determines the value of the spread - the difference between the best bid price and the best ask price. If the spread is large, short-term trading of a stock will be very expensive, so illiquid stocks are only suitable for long-term investing. In addition, if there is a need to buy or sell a significant amount of volume, it may take some time for a low-liquidity stock, or it may result in additional slippage losses.
Therefore, if you are going to trade actively enough, you will have to limit yourself to the list of more or less liquid shares. And the more active trading is planned, the stronger are the requirements to liquidity. For intraday trading, for example, you will most likely have to limit yourself to a few of the most liquid shares - blue chips.