A share price is the amount it costs to buy one share of a company at a given moment. It is set by supply and demand in the market, not by the company, and it is the number quoted live on an exchange through the trading day.
Buyers and sellers meet in an order book, where the best buy price (the bid) and the best sell price (the ask) frame the current quote. The price moves on company news, earnings, sector trends, interest rates, and broad sentiment, so it can change second by second while the exchange is open.
A share price is not the same as a company's market capitalisation. The price values a single share, while market capitalisation values the whole company by multiplying that price by every share outstanding. A high share price on its own says nothing about a company's size, because a company can have few expensive shares or many cheap ones.
You watch a share quoted at a bid of USD 49.98 and an ask of USD 50.02. You buy 100 shares at the ask:
100 √ó USD 50.02 = USD 5,002
Your position is worth USD 5,002 at that moment. A USD 50 share is not a "smaller" company than a USD 500 one: with 50 million shares, the USD 50 company is worth USD 2.5 billion, more than a USD 500 company that has only 1 million shares.